The lower level async-as-state-machine (or coroutine or whatever) should be more standard, but that's an argument for another day. For now, you're right and the

The lower level async-as-state-machine (or coroutine or whatever) should be more standard, but that's an argument for another day. For now, you're right and the opaque threading model is basically what Go does. On the other hand, it's not suitable for Rust because in some ways Rust is lower level. C# went and did it the Rust way, which I personally appreciate but I understand fits into the problem you're describing.