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问题内容func main() {
// Start a long-running process, capture stdout and stderr
findCmd := cmd.NewCmd("find", "/", "--name", "needle")
statusChan := findCmd.Start() // non-blocking
ticker := time.NewTicker(2 * time.Second)
// Print last line of stdout every 2s
go func() { ------------ this keeps running in background, how do I stop this goroutine
for range ticker.C {
status := findCmd.Status()
n := len(status.Stdout)
if len > 10 {
findCmd.Stop() ------- at this point I want to stop this goroutine
}
fmt.Println(status.Stdout[n-1])
}
}()
// Stop command after 1 hour
go func() {
<-time.After(1 * time.Hour)
findCmd.Stop()
}()
// Check if command is done
select {
case finalStatus := <-statusChan:
// done
default:
// no, still running
}
// Block waiting for command to exit, be stopped, or be killed
finalStatus := <-statusChan
}
goroutine 用于每 2 秒打印一次 stdout 的最后一行,尝试了一些方法来停止 goroutine,但没有任何效果。 如何使用通道停止该 goroutine
正确答案
这就是使用 select, case 的地方。你可以这样做:
ticker := time.newticker(2 * time.second)
done := make(chan struct{})
// the go routine that you want to stop when needed
go func() {
select {
case <-ticker.c:
// do stuff
case <-done:
ticker.stop() // this is optional based on your purpose
}
}()
// do stuff
// stop above go routine
close(done) // when there are many go routine you want to stop as reading from closed channel return the channel zero value
// or
done <- struct{}{} // when there is only 1 go routine you want to stop
其中一个选项是将上下文传递给此类函数/特性。每当您传递上下文时,您都可以捕获取消信号并在选择语句中使用它。
func main() {
appctx := context.background()
// ...
ticker := time.newticker(2 * time.second)
tickerctx, tickercancel := context.withcancel(appctx) // create context for ticker, derive from root context
// print last line of stdout every 2s
go func(ctx context.context) {
for {
select {
case <-ticker.c: // tick!
// ...
// if you need to perform any operation requiring the context pass `ctx`.
// if case the ctx is canceled all operations should be terminated as well.
case <-ctx.done() // context has been cancelled
return
}
}
}(tickerctx)
// stop command after 1 hour
go func() {
<-time.after(1 * time.hour)
tickercancel()
}()
// ...
}
这样,我们就可以使用上下文,并且可以控制需要上下文的所有操作(我们可以随时取消它们)。
在您的情况下,可能还有另一个改进,在一段时间后终止基于 ctx 的操作(不需要使用另一个带有计时器的 goroutine):
func main() {
appCtx := context.Background()
// ...
ticker := time.NewTicker(2 * time.Second)
tickerCtx, tickerCancel := context.WithTimeout(appCtx, time.Duration(1) * time.Hour) // create a context with a timeout
// Print last line of stdout every 2s
go func(ctx context.Context) {
for {
select {
case <-ticker.C: // tick!
// ...
case <-ctx.Done() // context has been cancelled
return
}
}
}(tickerCtx)
// We don't need to run a new goroutine terminate the ctx. The timeout we set will do the job.
// ...
}
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