Kotlin has an interesting midpoint between async/await and built-in lightweight threads. With async/await calls are async by default and if you await them they

Kotlin has an interesting midpoint between async/await and built-in lightweight threads. With async/await calls are async by default and if you await them they become synchronous. In Kotlin and with built-in lightweight threads this is reversed, but in Kotlin the callee still has a different function signature depending on whether it uses async internally or not.