Kotlin coroutines are just async/await with different syntactic defaults. That is, when you call a `suspend fun` it is awaited by default, and if you want to ge

Kotlin coroutines are just async/await with different syntactic defaults. That is, when you call a `suspend fun` it is awaited by default, and if you want to get a promise/future/etc from it instead that's when you write an extra annotation. Rust went the way it did syntactically because annotating the await points lets you see them when reading a program, and possibly out of familiarity. Rust went the way it did implementation-wise (stackless rather than stackful) because it's more efficient.