Golang如何捕获网络请求错误

resp, err := http.Get("https://example.com")
if err != nil {
    log.Printf("请求失败: %v", err)
    return
}
defer resp.Body.Close()
if resp.StatusCode >= 400 {
log.Printf("HTTP错误: %d", resp.StatusCode)
}

client := &http.Client{
    Timeout: 10 * time.Second,
    Transport: &http.Transport{
        DialContext: (&net.Dialer{
            Timeout:   5 * time.Second,
            KeepAlive: 30 * time.Second,
        }).DialContext,
        TLSHandshakeTimeout: 5 * time.Second,
    },
}
resp, err := client.Get("https://slow-site.com")
if err != nil {
log.Printf("请求异常: %v", err)
// 常见错误类型：timeout, connection refused, EOF
}

resp, err := client.Do(req)
if err != nil {
    if errors.Is(err, context.DeadlineExceeded) {
        log.Println("请求超时")
    } else if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
        log.Println("网络超时")
    } else if strings.Contains(err.Error(), "connection refused") {
        log.Println("连接被拒绝")
    } else {
        log.Printf("未知错误: %v", err)
    }
    return
}

body, err := io.ReadAll(resp.Body)
if err != nil {
    log.Printf("读取响应体失败: %v", err)
    return
}
// 使用body...