跳出选择循环？

Question

我正在尝试使用select循环来接收消息或超时信号。如果收到超时信号，循环应该中止：

package main

import ("fmt"; "time")

func main() {

    done := time.After(1*time.Millisecond)

    numbers := make(chan int)

    go func() {for n:=0;; {numbers <- n; n++}}()

    for {

        select {

            case <-done:

                break

            case num := <- numbers:

                fmt.Println(num)

        }

    }

}

然而，它似乎并没有停止：

$ go run a.go

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[...]

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[...]

为什么？我用time.After错了吗？

Answer 1

Go规范说：“break”语句终止同一函数内最里面的“for”、“switch”或“select”语句的执行。在您的示例中，您只是脱离了 select 语句。如果您替换break为一条return语句，您将看到它正在运行。

Answer 2

在您的示例代码中， areturn似乎像 Pat 所说的那样合适，但为了将来参考，您可以使用标签：package mainimport (&nbsp; &nbsp; "fmt"&nbsp; &nbsp; "time")func main() {&nbsp; &nbsp; done := time.After(1 * time.Millisecond)&nbsp; &nbsp; numbers := make(chan int)&nbsp; &nbsp; // Send to channel&nbsp; &nbsp; go func() {&nbsp; &nbsp; &nbsp; &nbsp; for n := 0; ; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; numbers <- n&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; n++&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }()readChannel:&nbsp; &nbsp; for {&nbsp; &nbsp; &nbsp; &nbsp; select {&nbsp; &nbsp; &nbsp; &nbsp; case <-done:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; break readChannel&nbsp; &nbsp; &nbsp; &nbsp; case num := <-numbers:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; fmt.Println(num)&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; // Additional logic...&nbsp; &nbsp; fmt.Println("Howdy")}