Testing Kotlin Coroutines when using `newSingleThreadContext` (Thread is not being cleaned up)

coroutines-actor-close-thread-test.kt

import kotlinx.coroutines.experimental.channels.actor
import kotlinx.coroutines.experimental.channels.consumeEach
import kotlinx.coroutines.experimental.newSingleThreadContext
import kotlinx.coroutines.experimental.runBlocking

val threads: Set<Thread>
    get() = Thread.getAllStackTraces().keys

val threadNames: List<String>
    get() = threads.map { it.name }

fun main(args: Array<String>) = runBlocking {
    println("threads = $threadNames")

    val actor = actor<Int>(newSingleThreadContext("TestThread")) {
        println("actor start")
        consumeEach { item ->
            println("item = $item")
        }
        println("actor end")
    }

    println("threads = $threadNames")

    println("actor.close()")
    actor.close()

    println("threads = $threadNames")

    println("thread sleep")
    Thread.sleep(2_000L)

    println("threads = $threadNames")
}

output.txt

threads = [Signal Dispatcher, Reference Handler, Finalizer, main, Monitor Ctrl-Break]
actor start
threads = [TestThread, Signal Dispatcher, Reference Handler, Finalizer, main, Monitor Ctrl-Break]
actor.close()
actor end
threads = [TestThread, Signal Dispatcher, Reference Handler, Finalizer, main, Monitor Ctrl-Break]
thread sleep
threads = [TestThread, Signal Dispatcher, Reference Handler, Finalizer, main, Monitor Ctrl-Break]

Per @elizarov in #coroutines at https://kotlinlang.slack.com/:

You have explicitly close the context to release the thread for now. In the future this will not be needed, though (see Kotlin/kotlinx.coroutines#261)