[tobz]

I'd say that this is roughly the case with .NET, in terms of async/await.

IIRC, you're using a thread pool under the hood, and you sort of have to opt-in: if you're trying to write your own async code, for example, you need to schedule it in a way that's slightly more complicated than just saying `go myFunc()`, but it's possible.

As for the JVM, libraries like Akka and Quasar already provide this, although possibly not as performantly as if the runtime itself provided it?

[int_19h]

Strictly speaking, whether you're using the thread pool under the hood or not depends on the task scheduler, which is pluggable. The default one that new threads get is indeed going to dispatch to the thread pool (on different threads at that, not the same one). But it can be pretty much anything. Async/await doesn't really care about any of that, it just creates continuations for you, and hands them over to the scheduler.