.await
            .map_err(|_| ())
    }
    /// Close a channel.
    pub async fn close(&mut self, id: ChannelId) -> Result<(), ()> {
        self.sender
            .send((id, ChannelMsg::Close))

                    Some((id, ChannelMsg::Close)) => {
                        session.close(id);
                    }

    Close,