Function handle_message 

async fn handle_message<S>(
    socket: &mut ClientSocket<S>,
    state: &Arc<TransportState>,
    watching: &mut Watching,
    holds: &mut Holds<'_>,
    updates: &mut Option<(UnboundedReceiver<SeatUpdate>, bool)>,
    dictate: &mut Streaming,
    viewers: &mut Viewers,
    reads: &mut Reads,
    arrival: Arrival,
    client: ClientMessage,
) -> Result<()>
where
    S: Sink<Message, Error = Error> + Unpin + Send,

handle_client with the message already read, so a subscribe that queued behind a read off the loop takes the same path the socket’s own did.