Shutdown “worker” go routine after buffer is empty

Question

I want my go routine worker (ProcessToDo() in the code below) to wait until all \"queued\" work is processed before shutting down.

The worker routine

Answer 1

It's usually a bad idea to have a consumer of a channel close it, since sending on a closed channel is a panic.

In this case, if you never want to interrupt the consumer before all messages have been sent, just use a for...range loop and close the channel when you're done. You will also need a signal like a WaitGroup to wait for the goroutine to finish (rather than using time.Sleep)

http://play.golang.org/p/r97vRPsxEb

var wg sync.WaitGroup

func ProcessToDo(todo chan string) {
    defer wg.Done()
    for work := range todo {
        fmt.Printf("todo: %q\n", work)
        time.Sleep(100 * time.Millisecond)

    }
    fmt.Printf("Shutting down ProcessToDo - todo channel closed!\n")

}

func main() {
    todo := make(chan string, 100)
    wg.Add(1)
    go ProcessToDo(todo)

    for i := 0; i < 20; i++ {
        todo <- fmt.Sprintf("Message %02d", i)
    }

    fmt.Println("*** all messages queued ***")
    close(todo)
    wg.Wait()
}