Function spawn_stream_handler 

pub fn spawn_stream_handler<P, F, Fut>(client: &Arc<Client>, f: F) -> P
where
    P: Proxy,
    F: FnMut(Request<P::Protocol>) -> Fut + 'static + Send,
    Fut: Future<Output = ()> + 'static + Send,

Utility that spawns a new task to handle requests of a particular type. The request handler must be threadsafe. The requests are handled one at a time.