错误处理和重试逻辑在 Golang 函数与外部 API 交互中的作用

import "errors"

var ErrNotFound = errors.New("not found")

if errors.Is(err, ErrNotFound) {
    // 处理找不到的错误
}

import "github.com/jmoiron/sqlx"

db := sqlx.MustOpen("mysql", "user:password@tcp(localhost:3306)/database")

if err := db.Get(nil, "SELECT * FROM users WHERE id = ?", 10); err != nil {
    // 处理由基础 SQL 错误引起的错误
}

for i := 0; i < 3; i++ {
    if err := callAPI(); err != nil {
        time.Sleep(100 * time.Millisecond)
        continue
    }

    return nil
}

ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

for {
    if err := callAPI(ctx); err != nil {
        select {
        case <-ctx.Done():
            return err
        default:
            continue
        }
    }

    return nil
}

import (
    "context"
    "fmt"
    "io"
    "net/http"
    "time"
)

func FetchUsers(w io.Writer) error {
    ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
    defer cancel()

    req, err := http.NewRequestWithContext(ctx, http.MethodGet, "https://api.example.com/users", nil)
    if err != nil {
        return fmt.Errorf("error creating HTTP request: %w", err)
    }

    resp, err := http.DefaultClient.Do(req)
    if err != nil {
        return fmt.Errorf("error making HTTP request: %w", err)
    }
    defer resp.Body.Close()

    if resp.StatusCode != http.StatusOK {
        return fmt.Errorf("invalid HTTP response status code: %d", resp.StatusCode)
    }

    // 解析 JSON 响应并进行处理
    // ...

    return nil
}