Here is an exercise using channels and select in a goroutine. If the
disconnect channel is changed to a buffered channel the goroutine doesn't
run at all.
Why does changing from an unbuffered to a buffered channel prevent running
the goroutine?
* func SelectDemo(wg *sync.WaitGroup) { messageCh :=
make(chan int, 10) disconnectCh := make(chan struct{})
// go routine won't run if channel is buffered
//disconnectCh := make(chan struct{}, 1) defer
close(messageCh) defer close(disconnectCh) go func()
{ fmt.Println(" goroutine")
wg.Add(1) for { select {
case v := <-messageCh:
fmt.Println(v) case <-disconnectCh:
fmt.Println(" disconnectCh")
// empty the message channel before exiting
for { select {
case v := <-messageCh:
fmt.Println(v)
default:
fmt.Println(" disconnection, return")
wg.Done()
return }
} } }
}() fmt.Println("Sending ints") for i := 0; i <
10; i++ { messageCh <- i }
fmt.Println("Sending done") disconnectCh <- struct{}{} }*
Here's the code to call the function from main. I use the wait group to
assure that the goroutine completes before the program exits:
*wg := sync.WaitGroup{} ch09.SelectDemo(&wg) wg.Wait()*
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