golang-patterns

# Go 开发模式 用于构建健壮、高效和可维护应用程序的惯用 Go 模式与最佳实践。 ## 何时激活 * 编写新的 Go 代码时 * 审查 Go 代码时 * 重构现有 Go 代码时 * 设计 Go 包/模块时 ## 核心原则 ### 1. 简洁与清晰 Go 推崇简洁而非精巧。代码应该显而易见且易于阅读。 ```go // Good: Clear and direct func GetUser(id string) (*User, error) { user, err := db.FindUser(id) if err != nil { return nil, fmt.Errorf("get user %s: %w", id, err) } return user, nil } // Bad: Overly clever func GetUser(id string) (*User, error) { return func() (*User, error) { if u, e := db.FindUser(id); e == nil { return u, nil } else { return nil, e } }() } ``` ### 2. 让零值变得有用 设计类型时，应使其零值无需初始化即可立即使用。 ```go // Good: Zero value is useful type Counter struct { mu sync.Mutex count int // zero value is 0, ready to use } func (c *Counter) Inc() { c.mu.Lock() c.count++ c.mu.Unlock() } // Good: bytes.Buffer works with zero value var buf bytes.Buffer buf.WriteString("hello") // Bad: Requires initialization type BadCounter struct { counts map[string]int // nil map will panic } ``` ### 3. 接受接口，返回结构体 函数应该接受接口参数并返回具体类型。 ```go // Good: Accepts interface, returns concrete type func ProcessData(r io.Reader) (*Result, error) { data, err := io.ReadAll(r) if err != nil { return nil, err } return &Result{Data: data}, nil } // Bad: Returns interface (hides implementation details unnecessarily) func ProcessData(r io.Reader) (io.Reader, error) { // ... } ``` ## 错误处理模式 ### 带上下文的错误包装 ```go // Good: Wrap errors with context func LoadConfig(path string) (*Config, error) { data, err := os.ReadFile(path) if err != nil { return nil, fmt.Errorf("load config %s: %w", path, err) } var cfg Config if err := json.Unmarshal(data, &cfg); err != nil { return nil, fmt.Errorf("parse config %s: %w", path, err) } return &cfg, nil } ``` ### 自定义错误类型 ```go // Define domain-specific errors type ValidationError struct { Field string Message string } func (e *ValidationError) Error() string { return fmt.Sprintf("validation failed on %s: %s", e.Field, e.Message) } // Sentinel errors for common cases var ( ErrNotFound = errors.New("resource not found") ErrUnauthorized = errors.New("unauthorized") ErrInvalidInput = errors.New("invalid input") ) ``` ### 使用 errors.Is 和 errors.As 检查错误 ```go func HandleError(err error) { // Check for specific error if errors.Is(err, sql.ErrNoRows) { log.Println("No records found") return } // Check for error type var validationErr *ValidationError if errors.As(err, &validationErr) { log.Printf("Validation error on field %s: %s", validationErr.Field, validationErr.Message) return } // Unknown error log.Printf("Unexpected error: %v", err) } ``` ### 永不忽略错误 ```go // Bad: Ignoring error with blank identifier result, _ := doSomething() // Good: Handle or explicitly document why it's safe to ignore result, err := doSomething() if err != nil { return err } // Acceptable: When error truly doesn't matter (rare) _ = writer.Close() // Best-effort cleanup, error logged elsewhere ``` ## 并发模式 ### 工作池 ```go func WorkerPool(jobs <-chan Job, results chan<- Result, numWorkers int) { var wg sync.WaitGroup for i := 0; i < numWorkers; i++ { wg.Add(1) go func() { defer wg.Done() for job := range jobs { results <- process(job) } }() } wg.Wait() close(results) } ``` ### 用于取消和超时的 Context ```go func FetchWithTimeout(ctx context.Context, url string) ([]byte, error) { ctx, cancel := context.WithTimeout(ctx, 5*time.Second) defer cancel() req, err := http.NewRequestWithContext(ctx, "GET", url, nil) if err != nil { return nil, fmt.Errorf("create request: %w", err) } resp, err := http.DefaultClient.Do(req) if err != nil { return nil, fmt.Errorf("fetch %s: %w", url, err) } defer resp.Body.Close() return io.ReadAll(resp.Body) } ``` ### 优雅关闭 ```go func GracefulShutdown(server *http.Server) { quit := make(chan os.Signal, 1) signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM) <-quit log.Println("Shutting down server...") ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second) defer cancel() if err := server.Shutdown(ctx); err != nil { log.Fatalf("Server forced to shutdown: %v", err) } log.Println("Server exited") } ``` ### 用于协调 Goroutine 的 errgroup ```go import "golang.org/x/sync/errgroup" func FetchAll(ctx context.Context, urls []string) ([][]byte, error) { g, ctx := errgroup.WithContext(ctx) results := make([][]byte, len(urls)) for i, url := range urls { i, url := i, url // Capture loop variables g.Go(func() error { data, err := FetchWithTimeout(ctx, url) if err != nil { return err } results[i] = data return nil }) } if err := g.Wait(); err != nil { return nil, err } return results, nil } ``` ### 避免 Goroutine 泄漏 ```go // Bad: Goroutine leak if context is cancelled func leakyFetch(ctx context.Context, url string) <-chan []byte { ch := make(chan []byte) go func() { data, _ := fetch(url) ch <- data // Blocks forever if no receiver }() return ch } // Good: Properly handles cancellation func safeFetch(ctx context.Context, url string) <-chan []byte { ch := make(chan []byte, 1) // Buffered channel go func() { data, err := fetch(url) if err != nil { return } select { case ch <- data: case <-ctx.Done(): } }() return ch } ``` ## 接口设计 ### 小而专注的接口 ```go // Good: Single-method interfaces type Reader interface { Read(p []byte) (n int, err error) } type Writer interface { Write(p []byte) (n int, err error) } type Closer interface { Close() error } // Compose interfaces as needed type ReadWriteCloser interface { Reader Writer Closer } ``` ### 在接口使用处定义接口 ```go // In the consumer package, not the provider package service // UserStore defines what this service needs type UserStore interface { GetUser(id string) (*User, error) SaveUser(user *User) error } type Service struct { store UserStore } // Concrete implementation can be in another package // It doesn't need to know about this interface ``` ### 使用类型断言实现可选行为 ```go type Flusher interface { Flush() error } func WriteAndFlush(w io.Writer, data []byte) error { if _, err := w.Write(data); err != nil { return err } // Flush if supported if f, ok := w.(Flusher); ok { return f.Flush() } return nil } ``` ## 包组织 ### 标准项目布局 ```text myproject/ ├── cmd/ │ └── myapp/ │ └── main.go # 入口点 ├── internal/ │ ├── handler/ # HTTP 处理器 │ ├── service/ # 业务逻辑 │ ├── repository/ # 数据访问 │ └── config/ # 配置 ├── pkg/ │ └── client/ # 公共 API 客户端 ├── api/ │ └── v1/ # API 定义（proto, OpenAPI） ├── testdata/ # 测试夹具 ├── go.mod ├── go.sum └── Makefile ``` ### 包命名 ```go // Good: Short, lowercase, no underscores package http package json package user // Bad: Verbose, mixed case, or redundant package httpHandler package json_parser package userService // Redundant 'Service' suffix ``` ### 避免包级状态 ```go // Bad: Global mutable state var db *sql.DB func init() { db, _ = sql.Open("postgres", os.Getenv("DATABASE_URL")) } // Good: Dependency injection type Server struct { db *sql.DB } func NewServer(db *sql.DB) *Server { return &Server{db: db} } ``` ## 结构体设计 ### 函数式选项模式 ```go type Server struct { addr string timeout time.Duration logger *log.Logger } type Option func(*Server) func WithTimeout(d time.Duration) Option { return func(s *Server) { s.timeout = d } } func WithLogger(l *log.Logger) Option { return func(s *Server) { s.logger = l } } func NewServer(addr string, opts ...Option) *Server { s := &Server{ addr: addr, timeout: 30 * time.Second, // default logger: log.Default(), // default } for _, opt := range opts { opt(s) } return s } // Usage server := NewServer(":8080", WithTimeout(60*time.Second), WithLogger(customLogger), ) ``` ### 使用嵌入实现组合 ```go type Logger struct { prefix string } func (l *Logger) Log(msg string) { fmt.Printf("[%s] %s\n", l.prefix, msg) } type Server struct { *Logger // Embedding - Server gets Log method addr string } func NewServer(addr string) *Server { return &Server{ Logger: &Logger{prefix: "SERVER"}, addr: addr, } } // Usage s := NewServer(":8080") s.Log("Starting...") // Calls embedded Logger.Log ``` ## 内存与性能 ### 当大小已知时预分配切片 ```go // Bad: Grows slice multiple times func processItems(items []Item) []Result { var results []Result for _, item := range items { results = append(results, process(item)) } return results } // Good: Single allocation func processItems(items []Item) []Result { results := make([]Result, 0, len(items)) for _, item := range items { results = append(results, process(item)) } return results } ``` ### 为频繁分配使用 sync.Pool ```go var bufferPool = sync.Pool{ New: func() interface{} { return new(bytes.Buffer) }, } func ProcessRequest(data []byte) []byte { buf := bufferPool.Get().(*bytes.Buffer) defer func() { buf.Reset() bufferPool.Put(buf) }() buf.Write(data) // Process... return buf.Bytes() } ``` ### 避免在循环中进行字符串拼接 ```go // Bad: Creates many string allocations func join(parts []string) string { var result string for _, p := range parts { result += p + "," } return result } // Good: Single allocation with strings.Builder func join(parts []string) string { var sb strings.Builder for i, p := range parts { if i > 0 { sb.WriteString(",") } sb.WriteString(p) } return sb.String() } // Best: Use standard library func join(parts []string) string {