[exDM69]

Early on in Rust's history, it had something similar to Go's goroutines with n:m green thread scheduling and libuv for async everything. Some other languages (e.g. Haskell/GHC) also have this kind of system.

But this practically requires some kind of garbage collection and a fat runtime.

I think it was a good decision on the Rust team to abandon this and go for a low level systems programming language. Otherwise it would've been just another Go-like language that isn't really usable in low level systems programming.

Implementing portable async language features without a fat runtime or garbage collection is novel work so it's no wonder that it's taking its own sweet time to reach maturity.