Oh, lovely. I'll have to check out Kotlin's coroutines in more detail. So far I haven't seen many coroutine/green thread implementations I like. In fact the only one I like is Python's gevent since it's very non-intrusive and often works with existing libraries without modification, whereas Python's async/await or C# (I think) require every part to be aware of the coro (and unwind the stack when suspending)