wg-async VS rlimit

I believe the solution mentioned in rust-lang/wg-async is the way to go: Add traits like AsyncWrite, AsyncRead, Executor/Runtime to the std so that tokio/async-std can implement them.

This is a consequence of runtimes relying on global variables that their core future types are dependent on. Creating abstractions to solve this problem is one of the main goals of the the async working group [0].

[0]: https://github.com/rust-lang/wg-async

Provided the futures you're selecting over are cancellation safe the plain loop over select! should be fine. Multiple channels in particular are safe to select over - if you have futures that aren't cancellation safe, you can just wrap them up in a task on the end of a channel and then select on that.

I'd like to be able to write runtime agnostic async libs.

You might be interested in taking a look at and potentially participating in the "Async Vision Document"[1] which is an exercise the team is going through to collect feedback about the current state of the ecosystem and what the pain points are, as well as a way to lay doing what the desired future state of async Rust should be[2]. The process is happening, as you would expect, in the open and there's still time to influence it[3] if your concerns aren't yet addressed or even mentioned[4].

[1]: https://rust-lang.github.io/wg-async-foundations/vision.html

[2]: https://blog.rust-lang.org/2021/03/18/async-vision-doc.html

[3]: https://github.com/rust-lang/wg-async-foundations/pulls

[4]: https://github.com/rust-lang/wg-async-foundations/issues

Thanks for the feedback. I posted this comment to a relevant github issue, fyi.