Function spawn_metered 

pub fn spawn_metered<T, G, F>(operation: &'static str, guard: G, f: F)
where
    T: Send + 'static,
    G: Send + 'static,
    F: Future<Output = Result<T>> + Send + 'static,

Spawns a metered future without waiting for its result.

The task has the same panic isolation, metrics, and guard lifetime as run_metered, but its result is discarded.