code: func (t *proxySubsys) proxyToSite(
  	ctx *srv.ServerContext, site reversetunnel.RemoteSite, remoteAddr net.Addr, ch ssh.Channel) error {
  
  	conn, err := site.DialAuthServer()
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	t.log.Infof("Connected to auth server: %v", conn.RemoteAddr())
  
  	go func() {
  		var err error
  		defer func() {
  			t.close(err)
  		}()
  		defer ch.Close()
  		_, err = io.Copy(ch, conn)
  	}()
  	go func() {
  		var err error
  		defer func() {
  			t.close(err)
  		}()
  		defer conn.Close()
  		_, err = io.Copy(conn, srv.NewTrackingReader(ctx, ch))
  
  	}()
  
  	return nil
  }
docs: // proxyToSite establishes a proxy connection from the connected SSH client to the
  // auth server of the requested remote site