如何优雅的退出子goroutine

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package main

import (
	"context"
	"log"
	"sync"
	"time"
)
var waitgroup sync.WaitGroup

//子goroutine 1
func worker1(ctx context.Context){
	defer  waitgroup.Done()
	go worker2(ctx) //演示再去开一个子goroutine
	BREAK:
	  for{
		  select {
			  case <-ctx.Done():
				break BREAK
			  default:
		  }
		  log.Println("worker1 ...")
		  time.Sleep(1*time.Second)
		}
}

//子goroutine 2
func worker2(ctx context.Context){
BREAK:
	for{
		select {
		case <-ctx.Done():
			break BREAK
		default:
		}
		log.Println("worker2 ...")
		time.Sleep(1*time.Second)
	}
}

func main() {
	//创建一个context，并标记为根节点
	ctx ,cancel := context.WithCancel(context.Background())
	waitgroup.Add(1)
		go worker1(ctx) //启动一个子goroutine
	time.Sleep(time.Second * 5)
	cancel() //context内置方法，用于退出子goroutine
	waitgroup.Wait()
	//演示验证worker是否退出
	for{
		log.Println("over ...")
		time.Sleep(1*time.Second)
	}
}