Go 入门（26）：练习——HTTP 接口服务

更新时间：2026-09-01。本文是 languages/go/beginner/ 入门层第 26 篇，接 CLI 待办事项。综合练习写一个 HTTP 接口服务，用户管理 CRUD，数据存在内存里。用 Go 标准库 net/http，不加第三方框架。

需求

实现一个用户管理 RESTful 接口：

方法	路径	功能
GET	/users	列出所有用户
GET	/users/{id}	查询单个用户
POST	/users	创建用户
DELETE	/users/{id}	删除用户

数据存在内存中（map[string]User）。

用到的知识

• net/http 包启动 HTTP 服务
• encoding/json 序列化请求和响应
• io.ReadAll 读取请求体
• strings 包处理 URL 路径
• 结构体组织数据

实现

package main

import (
    "encoding/json"
    "fmt"
    "io"
    "log"
    "net/http"
    "strings"
)

type User struct {
    ID    string `json:"id"`
    Name  string `json:"name"`
    Email string `json:"email"`
}

var users = make(map[string]User)

func main() {
    // 初始数据
    users["1"] = User{ID: "1", Name: "Alice", Email: "alice@example.com"}
    users["2"] = User{ID: "2", Name: "Bob", Email: "bob@example.com"}

    http.HandleFunc("/users", usersHandler)
    http.HandleFunc("/users/", userHandler)

    log.Println("Server starting on :8080")
    log.Fatal(http.ListenAndServe(":8080", nil))
}

// GET /users - 列出所有用户
// POST /users - 创建用户
func usersHandler(w http.ResponseWriter, r *http.Request) {
    switch r.Method {
    case http.MethodGet:
        userList := make([]User, 0, len(users))
        for _, u := range users {
            userList = append(userList, u)
        }
        writeJSON(w, http.StatusOK, userList)

    case http.MethodPost:
        body, err := io.ReadAll(r.Body)
        if err != nil {
            writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid body"})
            return
        }
        var u User
        if err := json.Unmarshal(body, &u); err != nil {
            writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid json"})
            return
        }
        if u.ID == "" {
            writeJSON(w, http.StatusBadRequest, map[string]string{"error": "id required"})
            return
        }
        users[u.ID] = u
        writeJSON(w, http.StatusCreated, u)

    default:
        writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
    }
}

// GET /users/{id} - 查询单个用户
// DELETE /users/{id} - 删除用户
func userHandler(w http.ResponseWriter, r *http.Request) {
    id := strings.TrimPrefix(r.URL.Path, "/users/")
    if id == "" {
        writeJSON(w, http.StatusBadRequest, map[string]string{"error": "id required"})
        return
    }

    switch r.Method {
    case http.MethodGet:
        u, ok := users[id]
        if !ok {
            writeJSON(w, http.StatusNotFound, map[string]string{"error": "user not found"})
            return
        }
        writeJSON(w, http.StatusOK, u)

    case http.MethodDelete:
        _, ok := users[id]
        if !ok {
            writeJSON(w, http.StatusNotFound, map[string]string{"error": "user not found"})
            return
        }
        delete(users, id)
        writeJSON(w, http.StatusNoContent, nil)

    default:
        writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
    }
}

func writeJSON(w http.ResponseWriter, status int, data any) {
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(status)
    if data != nil {
        json.NewEncoder(w).Encode(data)
    }
}

运行和测试

go run main.go

# 另一个终端测试
curl http://localhost:8080/users
# [{"id":"1","name":"Alice","email":"alice@example.com"},...]

curl http://localhost:8080/users/1
# {"id":"1","name":"Alice","email":"alice@example.com"}

curl -X POST http://localhost:8080/users \
  -d '{"id":"3","name":"Charlie","email":"charlie@example.com"}'
# 201 Created

curl -X DELETE http://localhost:8080/users/3
# 204 No Content

扩展练习

1. 支持 PUT 更新用户
2. 改成文件持久化，重启后数据不丢失
3. 加一个中间件：打印每个请求的 Method、Path、耗时
4. 用结构体抽取写 response 的通用逻辑

相关与延伸

下一篇：练习：并发爬虫；net/http 底层是 goroutine-per-request 模型，每个请求开一个 goroutine 处理；Go 标准库的 HTTP 服务已经够用，进阶层讲中间件。

一句话总结

HTTP 接口服务：用 net/http 标准库就能写 RESTful 接口，http.HandleFunc 注册路由，r.Method 判断方法分发，json.NewEncoder/Decoder 处理 JSON 序列化；Go 标准库不依赖第三方框架就能写生产级服务。