Most network functions provide a way to provide a timeout or cancellation
explicitly. Listen is one such: see this method - if the context that it's
passed is cancelled, the Listen call will return.
https://pkg.go.dev/net#ListenConfig.Listen
The most general way to stop waiting on timeout or cancellation in the
absence of explicitly provided functionality is to start the function in a
separate goroutine and send notification when the function completes. This
is non-ideal because the goroutine will remain around even when the waiter
has given up, but can still be a useful technique in some circumstances.
Hope this helps,
rog.
On Sat, 16 Apr 2022, 14:30 Zhaoxun Yan, <yan.zhao...@gmail.com> wrote:
> Timeout is quite common practice in programming. For example, Listen
> function in internet connection with a timeout may just close the
> connection and Listen thread as silence persists for some period, like 60
> seconds.
>
> I found it very hard to implement such a general shutdown feature of a
> thread/goroutine on such I/O functions, here is one unsuccessful try, which
> I want to stop the whole in 9 seconds but it does not function as I wanted:
>
> package main
>
> import (
> "fmt"
> "time"
> )
>
> func wait(){
> time.Sleep(5 * time.Second)
> fmt.Println("wait 1st signal")
> time.Sleep(5 * time.Second)
> fmt.Println("wait 2nd signal")
> }
>
>
> func main() {
> ticker := time.NewTicker(3 * time.Second)
> i := 0
> for{
> select{
> case <- ticker.C:
> i++
> fmt.Printf("ticker rings %d\n", i)
> if i==3{
> return
> }
> default:
> wait()
> }
> }
>
> }
>
> The result is to wait whole 30 seconds:
> wait 1st signal
> wait 2nd signal
> ticker rings 1
> wait 1st signal
> wait 2nd signal
> ticker rings 2
> wait 1st signal
> wait 2nd signal
> ticker rings 3
>
> An online course suggests to wrap up the wait/Listen function with a
> channel (which would return something instead of nothing above)
>
> go func(){
> resultChan <- Listen()
> }()
>
> select{
> case a := <- resultChan:
> //analyze a
> case <-ticker.C:
> //might break or return
> }
>
> But this recipe obviously only kill the select goroutine rather than the
> anonymous goroutine that actually runs Listen function. My question is -
> how to kill the waiting or listening goroutine from outside?
>
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