I'm trying to simulate a time-consuming API call, ...

# coroutines

[Icyrockton]

I'm trying to simulate a time-consuming API call, but the program doesn't seem to terminate properly, the main thread is stuck, is this because resume is on another thread?

suspend fun a() { println("call a") }
suspend fun b() { println("call b") }
val executor = Executors.newSingleThreadScheduledExecutor()

suspend fun test() {
    println(Thread.currentThread().name)
    a()
    val g = suspendCoroutine<Int> { continuation ->
        executor.schedule({
            println("call resume!!! ${Thread.currentThread().name}")
            continuation.resume(20)
        }, 1, TimeUnit.SECONDS)
        COROUTINE_SUSPENDED
    }
    println(g)
    b()
}

suspend fun main() {
    test()
    println("test done!")
}

[Sam]

Actually it's just because your executor has some threads that are still running. If you need to use a custom executor, remember to call executor.shutdown() once all your tasks are submitted.

[Sam]

By the way, what's COROUTINE_SUSPENDED doing in there? That looks like an internal symbol that doesn't belong in ordinary code like this.

[Icyrockton]

Thanks! it's helpful!
Yeah, I know. I'm just learning the internal things of coroutines