Go App Engine中urlfetch进行POST请求的正确姿势

package main

import (
    "context" // 对于现代Go App Engine开发，推荐使用标准库的context
    "io"
    "log"
    "net/http"
    "strings"

    "google.golang.org/appengine" // 如果需要获取App Engine上下文
    "google.golang.org/appengine/urlfetch" // 核心包
)

func handler(w http.ResponseWriter, r *http.Request) {
    ctx := appengine.NewContext(r) // 获取App Engine上下文
    // ... 后续操作将使用这个ctx
}

func makePostRequest(ctx context.Context, targetURL string, requestBody string, contentType string) (string, error) {
    // 1. 使用urlfetch.Client创建HTTP客户端
    client := urlfetch.Client(ctx)

    // 2. 准备请求体
    bodyReader := strings.NewReader(requestBody)

    // 3. 使用客户端的Post方法发送请求
    resp, err := client.Post(targetURL, contentType, bodyReader)
    if err != nil {
        log.Printf("Error sending POST request: %v", err)
        return "", err
    }
    defer resp.Body.Close()

    // 4. 处理响应
    if resp.StatusCode != http.StatusOK {
        log.Printf("Received non-OK status code: %d", resp.StatusCode)
        return "", http.Errorf("Received non-OK status code: %d", resp.StatusCode)
    }

    responseBody, err := io.ReadAll(resp.Body)
    if err != nil {
        log.Printf("Error reading response body: %v", err)
        return "", err
    }

    return string(responseBody), nil
}

package main

import (
    "context"
    "fmt"
    "io"
    "log"
    "net/http"
    "strings"

    "google.golang.org/appengine"
    "google.golang.org/appengine/urlfetch"
)

func init() {
    http.HandleFunc("/", handler)
}

func handler(w http.ResponseWriter, r *http.Request) {
    ctx := appengine.NewContext(r) // 获取App Engine上下文

    targetURL := "https://jsonplaceholder.typicode.com/posts" // 示例目标URL
    postData := `{"title": "foo", "body": "bar", "userId": 1}`
    contentType := "application/json"

    log.Printf("Attempting to send POST request to %s with data: %s", targetURL, postData)

    responseBody, err := makePostRequest(ctx, targetURL, postData, contentType)
    if err != nil {
        http.Error(w, fmt.Sprintf("Failed to make POST request: %v", err), http.StatusInternalServerError)
        return
    }

    fmt.Fprintf(w, "POST request successful! Response:\n%s", responseBody)
}

// makePostRequest 封装了使用urlfetch.Client发送POST请求的逻辑
func makePostRequest(ctx context.Context, targetURL string, requestBody string, contentType string) (string, error) {
    client := urlfetch.Client(ctx) // 关键：使用urlfetch.Client初始化

    bodyReader := strings.NewReader(requestBody)

    resp, err := client.Post(targetURL, contentType, bodyReader)
    if err != nil {
        return "", fmt.Errorf("error sending POST request: %w", err)
    }
    defer resp.Body.Close()

    if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated { // 200 OK 或 201 Created
        return "", fmt.Errorf("received non-successful status code: %d - %s", resp.StatusCode, resp.Status)
    }

    responseBytes, err := io.ReadAll(resp.Body)
    if err != nil {
        return "", fmt.Errorf("error reading response body: %w", err)
    }

    return string(responseBytes), nil
}