Kotlinのcoroutinesの挙動を確認する

fun process(i: Int) {
    println("Work $i start")
    Thread.sleep(1000)
    println("Work $i done")
}

fun postProcess() {
    println("Waiting start")
    Thread.sleep(2500)
    println("Waiting done")
}

fun main() {
    repeat(2) {
        process(it)
    }
}

Work 0 start
Work 0 done
Work 1 start
Work 1 done

fun main() {
    repeat(2) {
        GlobalScope.launch {
            process(it)
        }
    }
    postProcess()
}

Waiting start
Work 1 start
Work 0 start
Work 1 done
Work 0 done
Waiting done

This is a delicate API and its use requires care.
Make sure you fully read and understand documentation of the declaration that is marked as a delicate API.

@OptIn(DelicateCoroutinesApi::class)
fun main() {
    ...
}

fun main() {
    repeat(2) {
        CoroutineScope(Dispatchers.IO).launch {
            process(it)
        }
    }
    postProcess()
}

Waiting start
Work 1 start
Work 0 start
Work 0 done
Work 1 done
Waiting done