Function run_worker 

pub async fn run_worker<E, T, H>(
    queue: Arc<Queue<E>>,
    config: WorkerConfig,
    handler: H,
    shutdown: Receiver<()>,
) -> JoinHandle<()>
where
    E: TitoEngine + 'static,
    T: EventType + Serialize + DeserializeOwned,
    H: Fn(QueueEvent<T>) -> BoxFuture<'static, Result<(), TitoError>> + Clone + Send + Sync + 'static,