Rust had that, but decided it wasn’t a good enough fit. Which was the motivation to keep exploring and land on the current async implementation which scales from embedded to servers with minimal overhead.

History:

This RFC proposes to remove the runtime system that is currently part of the standard library, which currently allows the standard library to support both native and green threading.

https://github.com/rust-lang/rfcs/blob/master/text/0230-remo...