package main

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

func main() {
	ctx1, cancel1 := context.WithCancel(context.Background())
	ctx2, cancel2 := context.WithCancel(context.Background())
	ctx3, _ := context.WithCancel(context.Background())
	go watch(ctx1, "任务1")
	go watch(ctx2, "任务2")
	go watch(ctx3, "任务3")
	time.Sleep(3 * time.Second)
	cancel1()
	cancel2()
	time.Sleep(3 * time.Second)
}
func watch(ctx context.Context, name string) {
	for {
		select {
		case <-ctx.Done():
			fmt.Println(name, "exited..")
			return
		default:
			fmt.Println(name, "runing...")
			time.Sleep(2 * time.Second)
		}
	}
}