Macro async_scope 

macro_rules! async_scope {
    ($scope:ident, $body:block) => { ... };
}

Available on crate feature alloc only.

Runs a body with a local asynchronous cleanup scope.

After the body completes, registered actions run before its value is returned. A return or ? exits the body future, so cleanup still runs. Panicking or dropping the returned future may leave cleanup actions unrun.