Go 后端开发实战指南：从入门到生产部署

// 启动一个 Goroutine
go func() {
    fmt.Println("Hello from goroutine")
}()

// 无缓冲 channel — 发送和接收同步阻塞
ch := make(chan int)
go func() { ch <- 42 }()
val := <-ch // 阻塞直到收到值

// 有缓冲 channel — 异步，缓冲区满/空时才阻塞
buffered := make(chan string, 10)
buffered <- "task" // 不阻塞（缓冲区未满）

select {
case msg := <-ch1:
    fmt.Println("received:", msg)
case <-time.After(3 * time.Second):
    fmt.Println("timeout")
case <-done:
    fmt.Println("shutting down")
}

func main() {
    http.HandleFunc("/api/hello", func(w http.ResponseWriter, r *http.Request) {
        w.Header().Set("Content-Type", "application/json")
        json.NewEncoder(w).Encode(map[string]string{"message": "Hello, Go!"})
    })

    server := &http.Server{
        Addr:         ":8080",
        ReadTimeout:  10 * time.Second,
        WriteTimeout: 10 * time.Second,
    }
    log.Fatal(server.ListenAndServe())
}

type Handler interface {
    ServeHTTP(ResponseWriter, *Request)
}

myproject/
├── cmd/                    # 可执行程序入口
│   └── server/
│       └── main.go
├── internal/               # 不对外暴露的内部包
│   ├── handler/            # HTTP 处理器
│   ├── service/            # 业务逻辑层
│   ├── repository/         # 数据访问层
│   └── middleware/         # 中间件
├── pkg/                    # 可被外部项目引用的共享库
│   ├── response/           # 统一响应格式
│   └── validator/          # 校验工具
├── config/                 # 配置定义与加载
├── migrations/             # 数据库迁移文件
├── scripts/                # 构建/部署脚本
├── api/                    # API 定义（OpenAPI/Protobuf）
├── Makefile
├── go.mod
├── go.sum
└── Dockerfile

type User struct {
    ID        uint           `gorm:"primarykey"`
    Name      string         `gorm:"size:100;not null;index"`
    Email     string         `gorm:"uniqueIndex;size:255"`
    Age       int            `gorm:"default:0"`
    Status    int            `gorm:"default:1"`
    CreatedAt time.Time
    UpdatedAt time.Time
    DeletedAt gorm.DeletedAt `gorm:"index"`
}

// 定义接口
type UserService interface {
    Create(ctx context.Context, user *User) error
    GetByID(ctx context.Context, id uint) (*User, error)
    List(ctx context.Context, page, size int) ([]User, int64, error)
    Update(ctx context.Context, user *User) error
    Delete(ctx context.Context, id uint) error
}

type UserHandler struct {
    svc UserService // 依赖接口而非具体实现
}

// 测试时注入 mock
type mockUserService struct{}

func (m *mockUserService) Create(ctx context.Context, user *User) error {
    return nil
}
// ... 实现其他方法

// 基础模式
result, err := doSomething()
if err != nil {
    // 处理或包装错误
    return fmt.Errorf("doSomething failed: %w", err)
}

type AppError struct {
    Code    int    `json:"code"`
    Message string `json:"message"`
    Err     error  `json:"-"`
}

func (e *AppError) Error() string {
    return e.Message
}

func (e *AppError) Unwrap() error {
    return e.Err
}

// 错误码定义
var (
    ErrNotFound     = &AppError{Code: 404, Message: "资源不存在"}
    ErrUnauthorized = &AppError{Code: 401, Message: "未授权"}
    ErrInternal     = &AppError{Code: 500, Message: "服务器内部错误"}
)

func ErrorHandler() gin.HandlerFunc {
    return func(c *gin.Context) {
        c.Next()

        if len(c.Errors) > 0 {
            err := c.Errors.Last()

            var appErr *AppError
            if errors.As(err, &appErr) {
                c.JSON(appErr.Code, gin.H{
                    "error": appErr.Message,
                })
                return
            }

            c.JSON(http.StatusInternalServerError, gin.H{
                "error": "internal server error",
            })
        }
    }
}

func TestCreateUser(t *testing.T) {
    // 准备
    db := setupTestDB(t)      // 内存 SQLite
    repo := NewUserRepository(db)
    svc := NewUserService(repo)

    // 执行
    user := &User{Name: "张三", Email: "zhangsan@example.com", Age: 28}
    err := svc.Create(context.Background(), user)

    // 断言
    assert.NoError(t, err)
    assert.NotZero(t, user.ID)
}

func TestValidateEmail(t *testing.T) {
    tests := []struct {
        name  string
        email string
        valid bool
    }{
        {"正常邮箱", "user@example.com", true},
        {"无 @ 符号", "userexample.com", false},
        {"空字符串", "", false},
        {"带加号", "user+tag@example.com", true},
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            valid := validateEmail(tt.email)
            assert.Equal(t, tt.valid, valid)
        })
    }
}

func BenchmarkJSONMarshal(b *testing.B) {
    user := User{Name: "张三", Email: "test@example.com", Age: 30}
    for i := 0; i < b.N; i++ {
        _, _ = json.Marshal(user)
    }
}

func TestUserHandler_GetUser(t *testing.T) {
    // 构建测试路由
    router := gin.New()
    handler := NewUserHandler(mockService)
    router.GET("/api/v1/users/:id", handler.GetUser)

    // 发起请求
    w := httptest.NewRecorder()
    req, _ := http.NewRequest("GET", "/api/v1/users/1", nil)
    router.ServeHTTP(w, req)

    // 验证响应
    assert.Equal(t, 200, w.Code)
    assert.Contains(t, w.Body.String(), "张三")
}

// 定义具体任务
type EmailJob struct {
    To      string
    Subject string
    Body    string
}

func (j *EmailJob) Execute(ctx context.Context) error {
    log.Printf("Sending email to %s: %s", j.To, j.Subject)
    // 模拟耗时操作
    time.Sleep(100 * time.Millisecond)
    return nil
}

func main() {
    pool := worker.NewPool(5, 100) // 5 个 worker，缓冲区 100
    pool.Start()

    for i := 0; i < 20; i++ {
        pool.Submit(&EmailJob{
            To:      fmt.Sprintf("user%d@example.com", i),
            Subject: "Welcome!",
            Body:    "Thank you for registering.",
        })
    }

    pool.Shutdown()
}

# Linux 平台编译
GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -ldflags="-s -w" -o server ./cmd/server

# macOS 编译
GOOS=darwin GOARCH=amd64 go build -o server ./cmd/server

# ARM 架构（树莓派等）
GOOS=linux GOARCH=arm64 go build -o server ./cmd/server

# ========== 构建阶段 ==========
FROM golang:1.22-alpine AS builder

WORKDIR /app
COPY go.mod go.sum ./
RUN go mod download

COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build \
    -ldflags="-s -w" \
    -o /app/server ./cmd/server

# ========== 运行阶段 ==========
FROM alpine:3.19

# 安装 CA 证书（用于 HTTPS 请求）
RUN apk --no-cache add ca-certificates tzdata

WORKDIR /app
COPY --from=builder /app/server .

# 使用非 root 用户运行
RUN adduser -D -H -h /app appuser
USER appuser

EXPOSE 8080
ENTRYPOINT ["./server"]