使用context关闭协程以及协程中的协程

package main

import (
	"sync"
	"context"
	"fmt"
	"time"
)

var wg sync.WaitGroup

func worker2(ctx context.Context) {
	LOOP:
		for {
			fmt.Printf("worker2\n")
			time.Sleep(time.Second)
			select {
			case <- ctx.Done():
				break LOOP
			default:
			}
		}
}

func worker(ctx context.Context) {
	go worker2(ctx)
	LOOP:
		for {
			fmt.Printf("worker\n")
			time.Sleep(time.Second)
			select {
			case <- ctx.Done():
				break LOOP
			default:

			}
		}
	wg.Done()
}

func main() {
	ctx := context.Background()
	ctx, cancel := context.WithCancel(ctx)
	wg.Add(1)
	go worker(ctx)
	//time.Sleep(time.Second*3)
	cancel()
	wg.Wait()
}