浅析Go语言中的超时控制

func main() {
	fmt.Println(time.Now())
	x := <-time.After(3 * time.Second)
	fmt.Println(x)
}

func main() {
	ch := make(chan struct{}, 1)
	go func() {
		fmt.Println("do something...")
		time.Sleep(4*time.Second)
		ch<- struct{}{}
	}()
	select {
	case <-ch:
		fmt.Println("done")
	case <-time.After(3*time.Second):
		fmt.Println("timeout")
	}
}

ch := make(chan string)
	timeout, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()
	go func() {
		time.Sleep(time.Second * 4)
		ch <- "done"
	}()
	select {
	case res := <-ch:
		fmt.Println(res)
	case <-timeout.Done():
		fmt.Println("timout", timeout.Err())
	}

timout context deadline exceeded

func main() {
	total := 12
	var num int32
	log.Println("begin")
	ctx, cancelFunc := context.WithTimeout(context.Background(), 3*time.Second)
	for i := 0; i < total; i++ {
		go func() {
			//time.Sleep(3 * time.Second)
			atomic.AddInt32(&num, 1)
			if atomic.LoadInt32(&num) == 10 {
				cancelFunc()
			}
		}()
	}
	for i := 0; i < 5; i++ {
		go func() {
			select {
			case <-ctx.Done():
				log.Println("ctx1 done", ctx.Err())
			}
			for i := 0; i < 2; i++ {
				go func() {
					select {
					case <-ctx.Done():
						log.Println("ctx2 done", ctx.Err())
					}
				}()
			}
		}()
	}
	time.Sleep(time.Second*5)
	log.Println("end", ctx.Err())
	fmt.Printf("执行完毕 %v", num)
}

ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	if err := srv.Shutdown(ctx); err != nil {
		log.Fatal("Server Shutdown:", err)
	}
	log.Println("Server exiting")