When people say "async is viral" in Rust, they mean that once you make one function async, that change tends to ripple through the rest of your code. Any function that calls it usually has to become async as well so it can await the result. In turn, the callers of those functions often need to become async too.

This propagation can continue all the way up the call stack until you reach your application's entry point. The main exception is when you introduce an explicit synchronous-to-asynchronous boundary, such as by using block_on, which drives the future to completion without requiring the caller itself to be async.

I've done quite a bit of async programming and I can't quite figure out what people are complaining about here. Best I can tell, they just don't understand what async functions actually are.

Huh, that pretty cool actually. I need to play around and see if this works with gtk-rs, channels get fairly annoying if you need to use them a lot.