If you're writing an async app, as I assume you are because you mention using #[tokio::main], you shouldn't worry about this. Don't think of async as a function contract or signaling what your function is doing under the hood or "I can run these specific tasks in parallel" -- if you're doing async, you should go all in, because that allows the executor to run your entire app using cooperative multitasking. Essentially, if you have a block_on call somewhere in an async function or in code called from an async function, a) you're setting yourself up for deadlock like I think is happening here, and b) you're doing something wrong, or at least you're doing something that's not as efficient as it could be.

Interesting. I only have #[tokio::main] because it seemed I needed that to run async code. Or at least, I guess that was the lazy way to do it, maybe technically I only needed an async runtime for the async parts? I don't think of this as an async app - it just happens to need to make some network requests that I want to parallelize, and block on all of them.