如果在第一次迭代和第二次迭代之间有一小段时间

Question

In the code below, iterations are runned two times.
Is it possible that "test2 <- true" is runned at the moment which is just between the first iteration and the second iteration?
I mean, is there a change to send true to "test2" when the first iteration is ended and the second iteration is not started?

package main

import "log"
import "time"

func main() {
    test := make(chan bool, 1)
    test2 := make(chan bool, 1)

    go func() {
        for {
            select {
            case <-test:
                log.Println("test")
            case <-test2:
                log.Println("test2")
            }
        }
    }()

    test <- true
    time.Sleep(1)
    test2 <- true
    time.Sleep(1)
}

Answer 1

Yes. Since your channels are buffered and can hold 1 value. the main execution flow can continue without your anonymous goroutine reading the value you send to the test channel, and it can send a value on the test2 channel before the goroutine wakes up and read the value on the test channel.

This is unlikely to happen, since you have a time.Sleep() call there to normally give time for the goroutine to execute, but there's no telling what'll happen in a corner case of your machine being very busy, being power suspended at an (un)lucky time or other things you didn't think about.

If your test channel was unbuffered, the test <- true statement would block until your goroutine received the value, and there would at least be no possibility for the goroutine to receive from test2 before receiving anything from the test channel.