Macro task_local 

macro_rules! task_local {
    () => { ... };
    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty; $($rest:tt)*) => { ... };
    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty) => { ... };
}

Declares task-local keys, each a LocalKey.

nuclei::task_local! {
    static REQUEST_ID: u64;
}

REQUEST_ID
    .scope(7, async {
        assert_eq!(REQUEST_ID.get(), 7);
    })
    .await;