选择完成后，此FOR循环中断如何进行

Question

The following code waits for the 'results' channel to be empty and then the DEFAULT branch breaks to Label DONE.

Now the question: Why does this break the FOR LOOP?? It seems that the FOR loop would continue to skip to DEFAULT and never end.

WHAT IS BREAKING THE FOR LOOP.

The Output is as follows:

Break DONE

End For

---

...
DONE:
for {
    select { // Nonblocking
    case result := <-results:
        fmt.Printf("%s:%d:%s
", result.filename, result.lino,
            result.line)
    default:
        fmt.Println("Break DONE")
        break DONE
    }
    fmt.Println("END Select")
}
fmt.Println("End For")

Answer 1

The confusion comes from the idea that you're going to block there on the first case. That's not what happens. You iterate the select options indefinitely taking the one available until you encounter the break. In this case, it would indicate there is nothing to receive from the results channel on your first iteration so it automatically falls into the default cause, prints Break DONE and you're done.