``` // Message types for counterActor sealed class...

# coroutines

[jkbbwr]

// Message types for counterActor
sealed class CounterMsg
object IncCounter : CounterMsg() // one-way message to increment counter
class GetCounter(val response: SendChannel<Int>) : CounterMsg() // a request with reply

// This function launches a new counter actor
fun counterActor() = actor<CounterMsg>(CommonPool) {
    var counter = 0 // actor state
    for (msg in channel) { // iterate over incoming messages
        when (msg) {
            is IncCounter -> counter++
            is GetCounter -> msg.response.send(counter)
        }
    }
}

fun main(args: Array<String>) = runBlocking<Unit> {
    val counter = counterActor() // create the actor
    massiveRun(CommonPool) {
        counter.send(IncCounter)
    }
    val response = Channel<Int>()
    counter.send(GetCounter(response))
    println("Counter = ${response.receive()}")
    counter.close() // shutdown the actor
}