Macro task_local

macro_rules! task_local {
    (static $NAME:ident: $t:ty = $e:expr) => { ... };
}

A macro to create a static of type LocalKey.

This macro is intentionally similar to the thread_local!, and creates a static which has a get_mut method to access the data on a task.

The data associated with each task local is per-task, so different tasks will contain different values.