浅谈golang 中time.After释放的问题

// 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
}

package main
import "time"
func main() {
    for {
        <- time.After(10 * time.Nanosecond)
    }
}

package main
import "time"
func main() {
    for i := 0; i < 100; i++ {
        go func(){
            for {
                <- time.After(10 * time.Nanosecond)
            }
        }()
    }
    time.Sleep(1 * time.Hour)
}

select {
    case time.After(3*time.Second):
        return errTimeout
    case packet := packetChannel:
        // process packet.
}

package main
import "time"
func main() {
    for {
        select {
        case <-time.After(3 * time.Second):
        default:
        }
    }
}

package main
import "time"
func main() {
    for {
        t := time.NewTimer(3*time.Second)
        select {
        case <- t.C:
        default:
            t.Stop()
        }
    }
}

package main 
import (
	"fmt"
	"time"
)
 
func main() {
	ch := make(chan string, 2)//定义了缓冲长度2的通道，类型是字符串，可以连续写入2次数据
	go func(c chan string) {
		for i := 0; i < 3; i++ {
			str := fmt.Sprintf("%d", i)
			c <- str
			time.Sleep(time.Millisecond * 10)
		}
	}(ch)
	go func(c chan string) {
		for i := 10; i < 13; i++ {
			str := fmt.Sprintf("%d", i)
			c <- str
			time.Sleep(time.Millisecond * 10)
		}
	}(ch)
	timelate := 0 //定义超时次数
	for {
		time.Sleep(time.Millisecond * 2000) //每隔2秒读取下管道
		select {
		case i := <-ch:
			fmt.Println("通道读取到:", i)
		case <-time.After(time.Second * 2): // 等待2秒超时，这里time.After 返回一个只读通道，就是当前时间值
			timelate++
			fmt.Printf("通道接收超时,第%d次\n", timelate)
			if timelate > 2 {
				goto end
			}
		}
	}
end:
	fmt.Println("退出88")
}

package main 
import (
	"fmt"
	"time"
)
 
func main() {
	ch := make(chan string, 2) //定义了缓冲长度2的通道，类型是字符串，可以连续写入2次数据
	go func(c chan string) {
		for i := 0; i < 3; i++ {
			str := fmt.Sprintf("%d", i)
			c <- str
			time.Sleep(time.Millisecond * 10)
		}
	}(ch)
	go func(c chan string) {
		for i := 10; i < 13; i++ {
			str := fmt.Sprintf("%d", i)
			c <- str
			time.Sleep(time.Millisecond * 10)
		}
		time.Sleep(time.Millisecond * 1000) //专门给这个协程加个1秒的延时，让它晚退出会，好调用close关闭通道。
		close(c)
	}(ch)
	timelate := 0 //定义超时次数
	for {
		time.Sleep(time.Millisecond * 2000) //每隔2秒读取下管道
		select {
		case i, br := <-ch: //从通道里读取2个返回值，第2个是通道是否关闭的bool变量
			if !br { //如果是false，表示通道关闭
				fmt.Println("通道关闭了")
				goto end
			}
			fmt.Println("通道读取到:", i)
		case <-time.After(time.Second * 2): // 等待2秒超时，这里time.After 返回一个只读通道，就是当前时间值
			timelate++
			fmt.Printf("通道接收超时,第%d次\n", timelate)
			if timelate > 2 {
				goto end
			}
		}
	}
end:
	fmt.Println("退出88")
}