Expyron

Structopt is not maintained anymore: https://github.com/TeXitoi/structopt/issues/525 Its author recommends moving to clap v3.

Although you probably don't want to increase the MSRV that much for now, `VecDeque::new()` was made `const` in 1.68, so it'll be possible to remove `lazy_static`/`once_cell` usage altogether at some...

Why not forego lazy initialization altogether and use a constant initializer? `AtomicUsize::new`, `Mutex::new` and `VecDeque::new` are all const since at most Rust 1.68, so you don't even need to increase...