// Exported methods of QUICConn wait for the handshake to become blocked
	// before returning to the user.
	select {
	case c.quic.blockedc <- struct{}{}:
	case <-c.quic.cancelc:
		return c.sendAlertLocked(alertCloseNotify)
	}
	// The QUICConn reads from signalc to notify us that the handshake may
	// be able to proceed. (The QUICConn reads, because we close signalc to
	// indicate that the handshake has completed.)

	// "predict" closeNotify alerts.
	c.rawInput.Grow(needs + bytes.MinRead)
	_, err := c.rawInput.ReadFrom(&atLeastReader{r, int64(needs)})
	return err
}

// sendAlertLocked sends a TLS alert message.
func (c *Conn) sendAlertLocked(err alert) error {
	if c.quic != nil {
		return c.out.setErrorLocked(&net.OpError{Op: "local error", Err: err})
	}

	switch err {
	case alertNoRenegotiation, alertCloseNotify: