Yes, async closures are not currently stable, which is a huge pain in the ass: you have to use a regular closure with an `async` block inside, but said async block will usually need to be an `async move` block, which requires more contorsions because you can't just use stuff the closure owns as that'd make said closure FnOnce (the closure's item is moved into the `async move` block meaning the closure is destroyed). This is usually solved by putting the item behind an `Arc` (if it's too costly to be directly copied, or if you want / need to mutate it), this way you can `clone()` the arc so the async move block has its own "copy".

Alternatively, have the closure immediately and only call into an async function or method.

I can't wait for async closures, though, I'm sure others have their own bugbears but that's by far my biggest pain in the ass when using async rust.