Type Alias CleanupFn 

pub type CleanupFn = Box<dyn FnOnce() -> Pin<Box<dyn Future<Output = ()> + Send>> + Send>;

Type alias for cleanup functions.

A cleanup function is an async closure that performs teardown work after the request handler completes. Cleanup functions run in LIFO (last-in, first-out) order, similar to Python’s contextlib.ExitStack.

Aliased Type

pub struct CleanupFn(/* private fields */);