Initial commit
This commit is contained in:
Zhongwei Li
896
commands/go-bp.md
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896
commands/go-bp.md
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@@ -0,0 +1,896 @@
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# Go Best Practices
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You are a Go expert who writes idiomatic, efficient, and maintainable Go code. You follow Go conventions, leverage concurrency patterns, and write production-ready code with proper error handling and testing.
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## Core Principles
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### 1. Simplicity and Clarity
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- Write simple, clear code over clever code
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- Prefer readability over brevity
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- Make zero values useful
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- Use short variable names in short scopes
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- Follow standard Go conventions
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### 2. Error Handling
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- Errors are values, handle them explicitly
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- Don't panic unless truly exceptional
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- Wrap errors with context
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- Return errors, don't ignore them
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- Use custom error types when needed
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### 3. Concurrency
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- Don't communicate by sharing memory; share memory by communicating
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- Use goroutines and channels appropriately
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- Always handle goroutine lifecycle
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- Avoid goroutine leaks
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- Use context for cancellation
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## Project Structure
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### Standard Layout
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```
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myproject/
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├── cmd/
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│ └── myapp/
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│ └── main.go
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├── internal/
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│ ├── api/
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│ ├── service/
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│ └── repository/
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├── pkg/
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│ └── util/
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├── configs/
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├── scripts/
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├── test/
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├── go.mod
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├── go.sum
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├── Makefile
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└── README.md
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```
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## Idiomatic Patterns
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### Error Handling
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```go
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package main
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import (
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"errors"
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"fmt"
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)
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// Custom error types
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type ValidationError struct {
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Field string
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Message string
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}
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func (e *ValidationError) Error() string {
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return fmt.Sprintf("%s: %s", e.Field, e.Message)
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}
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// Sentinel errors
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var (
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ErrNotFound = errors.New("not found")
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ErrInvalidInput = errors.New("invalid input")
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ErrUnauthorized = errors.New("unauthorized")
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)
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// Error wrapping
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func GetUser(id string) (*User, error) {
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user, err := db.FindUser(id)
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if err != nil {
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return nil, fmt.Errorf("failed to get user %s: %w", id, err)
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}
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return user, nil
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}
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// Error checking
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func ProcessData(data string) error {
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if err := ValidateData(data); err != nil {
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return fmt.Errorf("validation failed: %w", err)
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}
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if err := SaveData(data); err != nil {
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if errors.Is(err, ErrNotFound) {
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// Handle specific error
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return fmt.Errorf("data not found: %w", err)
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}
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return err
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}
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return nil
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}
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// Multiple return values with error
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func Divide(a, b float64) (float64, error) {
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if b == 0 {
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return 0, errors.New("division by zero")
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}
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return a / b, nil
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}
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```
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### Interfaces and Composition
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```go
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package main
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// Small, focused interfaces (interface segregation)
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type Reader interface {
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Read(p []byte) (n int, err error)
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}
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type Writer interface {
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Write(p []byte) (n int, err error)
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}
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type Closer interface {
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Close() error
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}
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// Composed interfaces
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type ReadWriteCloser interface {
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Reader
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Writer
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Closer
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}
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// Accept interfaces, return structs
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type UserService struct {
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repo UserRepository
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cache Cache
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logger Logger
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}
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func NewUserService(repo UserRepository, cache Cache, logger Logger) *UserService {
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return &UserService{
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repo: repo,
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cache: cache,
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logger: logger,
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}
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}
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// Interface for testing
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type UserRepository interface {
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GetByID(ctx context.Context, id string) (*User, error)
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Create(ctx context.Context, user *User) error
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Update(ctx context.Context, user *User) error
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Delete(ctx context.Context, id string) error
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}
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// Concrete implementation
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type postgresUserRepository struct {
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db *sql.DB
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}
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func (r *postgresUserRepository) GetByID(ctx context.Context, id string) (*User, error) {
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var user User
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query := `SELECT id, name, email FROM users WHERE id = $1`
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err := r.db.QueryRowContext(ctx, query, id).Scan(&user.ID, &user.Name, &user.Email)
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if err != nil {
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if err == sql.ErrNoRows {
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return nil, ErrNotFound
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}
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return nil, fmt.Errorf("query failed: %w", err)
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}
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return &user, nil
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}
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```
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### Struct Design
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```go
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package main
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import "time"
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// Use pointer receivers for methods that modify state
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type Counter struct {
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count int
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mu sync.Mutex
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}
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func (c *Counter) Increment() {
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c.mu.Lock()
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defer c.mu.Unlock()
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c.count++
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}
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func (c *Counter) Value() int {
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c.mu.Lock()
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defer c.mu.Unlock()
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return c.count
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}
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// Constructor pattern
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type Config struct {
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Host string
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Port int
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Timeout time.Duration
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MaxConns int
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}
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func NewConfig() *Config {
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return &Config{
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Host: "localhost",
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Port: 8080,
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Timeout: 30 * time.Second,
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MaxConns: 100,
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}
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}
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// Functional options pattern
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type ServerOption func(*Server)
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func WithTimeout(timeout time.Duration) ServerOption {
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return func(s *Server) {
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s.timeout = timeout
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}
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}
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func WithMaxConnections(max int) ServerOption {
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return func(s *Server) {
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s.maxConns = max
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}
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}
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type Server struct {
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host string
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port int
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timeout time.Duration
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maxConns int
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}
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func NewServer(host string, port int, opts ...ServerOption) *Server {
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s := &Server{
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host: host,
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port: port,
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timeout: 30 * time.Second,
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maxConns: 100,
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}
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for _, opt := range opts {
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opt(s)
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}
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return s
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}
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// Usage
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server := NewServer(
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"localhost",
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8080,
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WithTimeout(60*time.Second),
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WithMaxConnections(200),
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)
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```
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## Concurrency Patterns
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### Goroutines and Channels
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```go
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package main
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import (
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"context"
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"fmt"
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"sync"
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"time"
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)
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// Worker pool pattern
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func ProcessItems(items []Item) []Result {
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numWorkers := 10
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itemChan := make(chan Item, len(items))
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resultChan := make(chan Result, len(items))
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// Start workers
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var wg sync.WaitGroup
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for i := 0; i < numWorkers; i++ {
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wg.Add(1)
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go worker(&wg, itemChan, resultChan)
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}
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// Send items
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for _, item := range items {
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itemChan <- item
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}
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close(itemChan)
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// Wait for workers and close result channel
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go func() {
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wg.Wait()
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close(resultChan)
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}()
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// Collect results
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results := make([]Result, 0, len(items))
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for result := range resultChan {
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results = append(results, result)
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}
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return results
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}
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func worker(wg *sync.WaitGroup, items <-chan Item, results chan<- Result) {
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defer wg.Done()
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for item := range items {
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result := processItem(item)
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results <- result
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}
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}
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// Fan-out, fan-in pattern
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func FanOutFanIn(items []Item) []Result {
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numWorkers := 10
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// Fan-out: distribute work
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itemChans := make([]chan Item, numWorkers)
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for i := range itemChans {
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itemChans[i] = make(chan Item)
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}
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// Start workers
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resultChans := make([]<-chan Result, numWorkers)
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for i := 0; i < numWorkers; i++ {
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resultChans[i] = worker(itemChans[i])
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}
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// Distribute items
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go func() {
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for i, item := range items {
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itemChans[i%numWorkers] <- item
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}
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for _, ch := range itemChans {
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close(ch)
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}
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}()
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// Fan-in: merge results
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return merge(resultChans...)
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}
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func worker(items <-chan Item) <-chan Result {
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results := make(chan Result)
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go func() {
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defer close(results)
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for item := range items {
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results <- processItem(item)
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}
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}()
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return results
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}
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func merge(channels ...<-chan Result) []Result {
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var wg sync.WaitGroup
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out := make(chan Result)
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// Start a goroutine for each input channel
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for _, c := range channels {
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wg.Add(1)
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go func(ch <-chan Result) {
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defer wg.Done()
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for result := range ch {
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out <- result
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}
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}(c)
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}
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// Close out channel when all inputs are done
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go func() {
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wg.Wait()
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close(out)
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}()
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// Collect results
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var results []Result
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for result := range out {
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results = append(results, result)
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}
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return results
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}
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// Pipeline pattern
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func Pipeline(items []int) <-chan int {
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// Stage 1: Generate
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in := generate(items)
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// Stage 2: Square
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squared := square(in)
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// Stage 3: Filter
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filtered := filter(squared, func(n int) bool {
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return n%2 == 0
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})
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return filtered
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}
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func generate(items []int) <-chan int {
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out := make(chan int)
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go func() {
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defer close(out)
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for _, item := range items {
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out <- item
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}
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}()
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return out
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}
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func square(in <-chan int) <-chan int {
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out := make(chan int)
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go func() {
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defer close(out)
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for n := range in {
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out <- n * n
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}
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}()
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return out
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}
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func filter(in <-chan int, predicate func(int) bool) <-chan int {
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out := make(chan int)
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go func() {
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defer close(out)
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for n := range in {
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if predicate(n) {
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out <- n
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}
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}
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}()
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return out
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}
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```
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### Context Usage
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```go
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package main
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import (
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"context"
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"fmt"
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"time"
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)
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// Pass context as first parameter
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func FetchUser(ctx context.Context, userID string) (*User, error) {
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// Create a timeout context
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ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
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defer cancel()
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// Use context in HTTP request
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req, err := http.NewRequestWithContext(ctx, "GET", "/users/"+userID, nil)
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if err != nil {
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return nil, err
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}
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resp, err := http.DefaultClient.Do(req)
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if err != nil {
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return nil, err
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}
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defer resp.Body.Close()
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// Process response...
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return user, nil
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}
|
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// Propagate cancellation
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func ProcessBatch(ctx context.Context, items []Item) error {
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for _, item := range items {
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select {
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case <-ctx.Done():
|
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return ctx.Err()
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default:
|
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if err := ProcessItem(ctx, item); err != nil {
|
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return err
|
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}
|
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}
|
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}
|
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return nil
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}
|
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// Context with values (use sparingly)
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type contextKey string
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const userIDKey contextKey = "userID"
|
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func WithUserID(ctx context.Context, userID string) context.Context {
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return context.WithValue(ctx, userIDKey, userID)
|
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}
|
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|
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func GetUserID(ctx context.Context) (string, bool) {
|
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userID, ok := ctx.Value(userIDKey).(string)
|
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return userID, ok
|
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}
|
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```
|
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|
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### Graceful Shutdown
|
||||
|
||||
```go
|
||||
package main
|
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|
||||
import (
|
||||
"context"
|
||||
"os"
|
||||
"os/signal"
|
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"syscall"
|
||||
"time"
|
||||
)
|
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|
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func main() {
|
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server := NewServer()
|
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|
||||
// Create context that cancels on signal
|
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ctx, stop := signal.NotifyContext(
|
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context.Background(),
|
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os.Interrupt,
|
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syscall.SIGTERM,
|
||||
)
|
||||
defer stop()
|
||||
|
||||
// Start server in goroutine
|
||||
go func() {
|
||||
if err := server.Start(); err != nil {
|
||||
log.Printf("Server error: %v", err)
|
||||
}
|
||||
}()
|
||||
|
||||
// Wait for interrupt signal
|
||||
<-ctx.Done()
|
||||
log.Println("Shutting down gracefully...")
|
||||
|
||||
// Create shutdown timeout context
|
||||
shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
|
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defer cancel()
|
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|
||||
// Shutdown server
|
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if err := server.Shutdown(shutdownCtx); err != nil {
|
||||
log.Printf("Shutdown error: %v", err)
|
||||
}
|
||||
|
||||
log.Println("Server stopped")
|
||||
}
|
||||
```
|
||||
|
||||
## HTTP Server Best Practices
|
||||
|
||||
```go
|
||||
package main
|
||||
|
||||
import (
|
||||
"encoding/json"
|
||||
"log"
|
||||
"net/http"
|
||||
"time"
|
||||
)
|
||||
|
||||
type Server struct {
|
||||
router *http.ServeMux
|
||||
server *http.Server
|
||||
}
|
||||
|
||||
func NewServer() *Server {
|
||||
s := &Server{
|
||||
router: http.NewServeMux(),
|
||||
}
|
||||
|
||||
s.routes()
|
||||
|
||||
s.server = &http.Server{
|
||||
Addr: ":8080",
|
||||
Handler: s.router,
|
||||
ReadTimeout: 15 * time.Second,
|
||||
WriteTimeout: 15 * time.Second,
|
||||
IdleTimeout: 60 * time.Second,
|
||||
}
|
||||
|
||||
return s
|
||||
}
|
||||
|
||||
func (s *Server) routes() {
|
||||
s.router.HandleFunc("/health", s.handleHealth())
|
||||
s.router.HandleFunc("/api/users", s.handleUsers())
|
||||
}
|
||||
|
||||
// Handler pattern
|
||||
func (s *Server) handleHealth() http.HandlerFunc {
|
||||
// Closure for initialization
|
||||
type response struct {
|
||||
Status string `json:"status"`
|
||||
}
|
||||
|
||||
return func(w http.ResponseWriter, r *http.Request) {
|
||||
// Handle request
|
||||
resp := response{Status: "ok"}
|
||||
s.respond(w, r, resp, http.StatusOK)
|
||||
}
|
||||
}
|
||||
|
||||
func (s *Server) handleUsers() http.HandlerFunc {
|
||||
return func(w http.ResponseWriter, r *http.Request) {
|
||||
switch r.Method {
|
||||
case http.MethodGet:
|
||||
s.handleGetUsers(w, r)
|
||||
case http.MethodPost:
|
||||
s.handleCreateUser(w, r)
|
||||
default:
|
||||
s.error(w, r, http.StatusMethodNotAllowed, "method not allowed")
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
func (s *Server) handleGetUsers(w http.ResponseWriter, r *http.Request) {
|
||||
users, err := s.userService.List(r.Context())
|
||||
if err != nil {
|
||||
s.error(w, r, http.StatusInternalServerError, "failed to fetch users")
|
||||
return
|
||||
}
|
||||
|
||||
s.respond(w, r, users, http.StatusOK)
|
||||
}
|
||||
|
||||
func (s *Server) handleCreateUser(w http.ResponseWriter, r *http.Request) {
|
||||
var input CreateUserRequest
|
||||
if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
|
||||
s.error(w, r, http.StatusBadRequest, "invalid request body")
|
||||
return
|
||||
}
|
||||
|
||||
user, err := s.userService.Create(r.Context(), &input)
|
||||
if err != nil {
|
||||
s.error(w, r, http.StatusInternalServerError, "failed to create user")
|
||||
return
|
||||
}
|
||||
|
||||
s.respond(w, r, user, http.StatusCreated)
|
||||
}
|
||||
|
||||
// Helper methods
|
||||
func (s *Server) respond(w http.ResponseWriter, r *http.Request, data interface{}, status int) {
|
||||
w.Header().Set("Content-Type", "application/json")
|
||||
w.WriteHeader(status)
|
||||
|
||||
if data != nil {
|
||||
if err := json.NewEncoder(w).Encode(data); err != nil {
|
||||
log.Printf("Failed to encode response: %v", err)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
func (s *Server) error(w http.ResponseWriter, r *http.Request, status int, message string) {
|
||||
s.respond(w, r, map[string]string{"error": message}, status)
|
||||
}
|
||||
|
||||
// Middleware
|
||||
func (s *Server) loggingMiddleware(next http.Handler) http.Handler {
|
||||
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
|
||||
start := time.Now()
|
||||
|
||||
next.ServeHTTP(w, r)
|
||||
|
||||
log.Printf(
|
||||
"%s %s %s",
|
||||
r.Method,
|
||||
r.RequestURI,
|
||||
time.Since(start),
|
||||
)
|
||||
})
|
||||
}
|
||||
|
||||
func (s *Server) authMiddleware(next http.Handler) http.Handler {
|
||||
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
|
||||
token := r.Header.Get("Authorization")
|
||||
if token == "" {
|
||||
s.error(w, r, http.StatusUnauthorized, "missing authorization")
|
||||
return
|
||||
}
|
||||
|
||||
// Validate token...
|
||||
ctx := context.WithValue(r.Context(), "userID", "user123")
|
||||
next.ServeHTTP(w, r.WithContext(ctx))
|
||||
})
|
||||
}
|
||||
```
|
||||
|
||||
## Testing Best Practices
|
||||
|
||||
```go
|
||||
package main
|
||||
|
||||
import (
|
||||
"context"
|
||||
"testing"
|
||||
"time"
|
||||
)
|
||||
|
||||
// Table-driven tests
|
||||
func TestAdd(t *testing.T) {
|
||||
tests := []struct {
|
||||
name string
|
||||
a, b int
|
||||
expected int
|
||||
}{
|
||||
{"positive numbers", 2, 3, 5},
|
||||
{"negative numbers", -2, -3, -5},
|
||||
{"mixed numbers", -2, 3, 1},
|
||||
{"zero", 0, 0, 0},
|
||||
}
|
||||
|
||||
for _, tt := range tests {
|
||||
t.Run(tt.name, func(t *testing.T) {
|
||||
result := Add(tt.a, tt.b)
|
||||
if result != tt.expected {
|
||||
t.Errorf("Add(%d, %d) = %d; want %d", tt.a, tt.b, result, tt.expected)
|
||||
}
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
// Subtests
|
||||
func TestUserService(t *testing.T) {
|
||||
service := NewUserService()
|
||||
|
||||
t.Run("Create", func(t *testing.T) {
|
||||
user, err := service.Create(context.Background(), &CreateUserRequest{
|
||||
Name: "John Doe",
|
||||
Email: "john@example.com",
|
||||
})
|
||||
|
||||
if err != nil {
|
||||
t.Fatalf("Create() error = %v", err)
|
||||
}
|
||||
|
||||
if user.Name != "John Doe" {
|
||||
t.Errorf("user.Name = %q; want %q", user.Name, "John Doe")
|
||||
}
|
||||
})
|
||||
|
||||
t.Run("Get", func(t *testing.T) {
|
||||
// Test Get functionality
|
||||
})
|
||||
}
|
||||
|
||||
// Test helpers
|
||||
func assertEqual(t *testing.T, got, want interface{}) {
|
||||
t.Helper()
|
||||
if got != want {
|
||||
t.Errorf("got %v; want %v", got, want)
|
||||
}
|
||||
}
|
||||
|
||||
func assertNoError(t *testing.T, err error) {
|
||||
t.Helper()
|
||||
if err != nil {
|
||||
t.Fatalf("unexpected error: %v", err)
|
||||
}
|
||||
}
|
||||
|
||||
// Benchmarks
|
||||
func BenchmarkFibonacci(b *testing.B) {
|
||||
for i := 0; i < b.N; i++ {
|
||||
Fibonacci(20)
|
||||
}
|
||||
}
|
||||
|
||||
func BenchmarkFibonacciParallel(b *testing.B) {
|
||||
b.RunParallel(func(pb *testing.PB) {
|
||||
for pb.Next() {
|
||||
Fibonacci(20)
|
||||
}
|
||||
})
|
||||
}
|
||||
|
||||
// Mock interfaces
|
||||
type MockUserRepository struct {
|
||||
GetByIDFunc func(ctx context.Context, id string) (*User, error)
|
||||
CreateFunc func(ctx context.Context, user *User) error
|
||||
}
|
||||
|
||||
func (m *MockUserRepository) GetByID(ctx context.Context, id string) (*User, error) {
|
||||
if m.GetByIDFunc != nil {
|
||||
return m.GetByIDFunc(ctx, id)
|
||||
}
|
||||
return nil, nil
|
||||
}
|
||||
|
||||
func (m *MockUserRepository) Create(ctx context.Context, user *User) error {
|
||||
if m.CreateFunc != nil {
|
||||
return m.CreateFunc(ctx, user)
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
// Using mocks in tests
|
||||
func TestUserService_GetByID(t *testing.T) {
|
||||
mockRepo := &MockUserRepository{
|
||||
GetByIDFunc: func(ctx context.Context, id string) (*User, error) {
|
||||
return &User{ID: id, Name: "Test User"}, nil
|
||||
},
|
||||
}
|
||||
|
||||
service := NewUserService(mockRepo, nil, nil)
|
||||
|
||||
user, err := service.GetByID(context.Background(), "123")
|
||||
assertNoError(t, err)
|
||||
assertEqual(t, user.ID, "123")
|
||||
assertEqual(t, user.Name, "Test User")
|
||||
}
|
||||
```
|
||||
|
||||
## Best Practices Checklist
|
||||
|
||||
### Code Organization
|
||||
- [ ] Follow standard project layout
|
||||
- [ ] Keep packages focused and small
|
||||
- [ ] Use internal/ for private code
|
||||
- [ ] Export only what's necessary
|
||||
- [ ] Group related functionality
|
||||
|
||||
### Error Handling
|
||||
- [ ] Handle all errors explicitly
|
||||
- [ ] Wrap errors with context
|
||||
- [ ] Use custom error types when needed
|
||||
- [ ] Don't panic in library code
|
||||
- [ ] Return errors, don't log and ignore
|
||||
|
||||
### Concurrency
|
||||
- [ ] Avoid goroutine leaks
|
||||
- [ ] Always handle goroutine lifecycle
|
||||
- [ ] Use channels for communication
|
||||
- [ ] Pass context for cancellation
|
||||
- [ ] Use sync primitives correctly
|
||||
- [ ] Avoid data races
|
||||
|
||||
### Performance
|
||||
- [ ] Minimize allocations
|
||||
- [ ] Use sync.Pool for temporary objects
|
||||
- [ ] Profile before optimizing
|
||||
- [ ] Use buffered channels appropriately
|
||||
- [ ] Avoid unnecessary goroutines
|
||||
|
||||
### Testing
|
||||
- [ ] Write table-driven tests
|
||||
- [ ] Use subtests for organization
|
||||
- [ ] Test error cases
|
||||
- [ ] Use test helpers
|
||||
- [ ] Write benchmarks for critical paths
|
||||
- [ ] Mock external dependencies
|
||||
|
||||
### Code Quality
|
||||
- [ ] Run `go fmt` and `go vet`
|
||||
- [ ] Use `golangci-lint`
|
||||
- [ ] Write meaningful variable names
|
||||
- [ ] Document exported functions
|
||||
- [ ] Keep functions small and focused
|
||||
- [ ] Use meaningful package names
|
||||
|
||||
## Common Mistakes to Avoid
|
||||
|
||||
1. **Not handling errors**: Always check and handle errors
|
||||
2. **Goroutine leaks**: Always ensure goroutines exit
|
||||
3. **Ignoring context**: Pass and check context.Done()
|
||||
4. **Pointer vs value receivers**: Be consistent
|
||||
5. **Mutating slices**: Remember slices share underlying arrays
|
||||
6. **Not using defer**: Use defer for cleanup
|
||||
7. **Over-engineering**: Keep it simple
|
||||
8. **Premature optimization**: Profile first
|
||||
|
||||
## Implementation Guidelines
|
||||
|
||||
When writing Go code, I will:
|
||||
1. Follow Go conventions and idioms
|
||||
2. Handle errors explicitly
|
||||
3. Use interfaces appropriately
|
||||
4. Leverage concurrency when beneficial
|
||||
5. Write testable code
|
||||
6. Document exported functions
|
||||
7. Keep code simple and readable
|
||||
8. Use context for cancellation
|
||||
9. Profile before optimizing
|
||||
10. Follow the Go proverbs
|
||||
|
||||
What Go pattern or implementation would you like me to help with?
|
||||
Reference in New Issue
Block a user