The implementation of a Fibonacci sequence using a producer is actually quite similar to the ones for iterators and sequences. You only need to replace yield() with send():

val context = newSingleThreadContext("myThread")

val fibonacci = produce(context) {
    send(1L)
    var current = 1L
    var next = 1L
    while (true) {
        send(next)
        val tmpNext = current + next
        current = next
        next = tmpNext
    }
}

fun main(args: Array<String>) = runBlocking {
    fibonacci.take(10).consumeEach {
        println(it)
    }
}

The previous example will print the first ten numbers produced: