package main

import (
	"errors"
	"fmt"
	"math/rand"
	"time"
)

// 模拟一个可能失败的操作
func mayFail() error {
	if rand.Float32() < 0.7 { // 70% 概率失败
		return errors.New("something went wrong")
	}
	return nil
}

func main() {
	const maxAttempts = 3
	attempt := 0

RETRY: // ← 标签：跳转点
	attempt++
	err := mayFail()
	if err != nil {
		fmt.Printf("attempt %d failed: %v\n", attempt, err)
		if attempt < maxAttempts {
			time.Sleep(time.Second) // 可选：做点延迟
			goto RETRY              // ← 关键：跳回标签
		}
		fmt.Println("all attempts exhausted, giving up")
		return
	}
	fmt.Printf("success on attempt %d!\n", attempt)
}