And note that it's a good thing that crates are async, because async-in-sync using block_on has only some potential small CPU time overhead, while sync-in-async

And note that it's a good thing that crates are async, because async-in-sync using block_on has only some potential small CPU time overhead, while sync-in-async requires having a thread for each concurrent usage and has potentially catastrophic memory overhead since a user and kernel mode stacks and thread data structures could in some cases be 100-1000x bigger than the future; hence, an async-only create is much better than a sync-only crate (although of course a crate that supports both is ideal from the user's point of view).