go语言--time.After

go语言--time.After

https://blog.csdn.net/cyk2396/article/details/78873396

1.源码分析：

**

// After waits for the duration to elapse and then sends the current time

// on the returned channel.

// It is equivalent to NewTimer(d).C.

// The underlying Timer is not recovered by the garbage collector

// until the timer fires. If efficiency is a concern, use NewTimer

// instead and call Timer.Stop if the timer is no longer needed.

func After(d Duration) <-chan Time {

return NewTimer(d).C

} **

根据注释可知，在等待给定的一段时间后，向返回值发送当前时间，返回值是一个单向只读通道

2.demo：

func main() {
	c := make(chan int, 1)
	select {
	case m := <-c:
		fmt.Println(m)
	case d := <-time.After(5 * time.Second):
		fmt.Println("time out")
		fmt.Println("current Time :", d)
	}

}

time out

current Time : 2017-12-22 15:04:05.0462009 +0800 CST m=+5.004000001

3.分析:

第一个case中，通道c一直处于阻塞状态;第二个case中，在time.After()结束后，从返回值通道中取出一个值赋予了d，该值就是当前时间