To create a producer, the coroutine builder produce() must be called. It returns a ReceiveChannel<E>. Because producers are built on top of channels, to yield elements in a producer, you use the function send(E):

val producer = produce {
    send(1)
}

It's possible to specify a CoroutineContext in the same way that you would with launch() or async():

val context = newSingleThreadContext("myThread")

val producer = produce(context) { 
    send(1)
}

Similar to iterators and sequences, you can specify a type, and it will work as long as the elements being emitted are compliant with it:

val producer : ReceiveChannel<Any> = produce(context) {
    send(5)
    send("a")
}