Function subscription_task 

pub(super) async fn subscription_task<C: JsonRpcCodec>(
    send: RequestStream<SendStream<Bytes>, Bytes>,
    reader: H3Reader<C>,
    unsub_rx: Receiver<Value>,
    sub: Arc<Subscription>,
    decoder: NotificationDecoder,
) -> Result<()>

Forward notifications to the subscription until the stream ends or an unsubscribe request arrives. The unsubscribe goes out on the same stream, so the server handles it with the subscription’s channel.