Kotlin ReceiverChannel example with background and "UI" threads.

main.kt

package testkotlin

import kotlinx.coroutines.experimental.channels.ReceiveChannel
import kotlinx.coroutines.experimental.channels.consumeEach
import kotlinx.coroutines.experimental.channels.produce
import kotlinx.coroutines.experimental.newFixedThreadPoolContext
import kotlinx.coroutines.experimental.newSingleThreadContext
import kotlinx.coroutines.experimental.runBlocking
import kotlinx.coroutines.experimental.withContext
import kotlin.coroutines.experimental.CoroutineContext


val bgContext = newFixedThreadPoolContext(4, "BG")
val uiContext = newSingleThreadContext("UI")

fun main(args: Array<String>): Unit = runBlocking {

    val squares = produceSquares(bgContext)
    squares.consumeEach {
        withContext(uiContext) {
            println("[${Thread.currentThread().name}] - Consumed: $it")
        }
    }
}

fun produceSquares(context: CoroutineContext): ReceiveChannel<Int> = produce(context) {
    for (x in 1..5) {
        val y = x * x
        println("[${Thread.currentThread().name}] - Produced: $y")
        send(y)
    }
}

output.txt

[BG-2] - Produced: 1
[BG-2] - Produced: 4
[UI] - Consumed: 1
[BG-2] - Produced: 9
[UI] - Consumed: 4
[BG-3] - Produced: 16
[UI] - Consumed: 9
[BG-4] - Produced: 25
[UI] - Consumed: 16
[UI] - Consumed: 25

Process finished with exit code 0