func (e AlertError) Error() string {
	return alert(e).String()
}

type alert uint8

const (
	// alert level
	alertLevelWarning = 1
	alertLevelError   = 2
)

const (
	alertCloseNotify                  alert = 0
	alertUnexpectedMessage            alert = 10
	alertBadRecordMAC                 alert = 20
	alertDecryptionFailed             alert = 21
	alertRecordOverflow               alert = 22

	cli.conn.SetTransportParameters(nil)
	cli.conn.Start(context.Background())
	for cli.conn.NextEvent().Kind != QUICNoEvent {
	}
	err := cli.conn.Close()
	if !errors.Is(err, alertCloseNotify) {
		t.Errorf("conn.Close() = %v, want alertCloseNotify", err)
	}
}

func TestQUICCanceledWaitingForTransportParams(t *testing.T) {
	config := testConfig.Clone()
	config.MinVersion = VersionTLS13

	// channel-binding value.
	clientFinishedIsFirst bool

	// closeNotifyErr is any error from sending the alertCloseNotify record.
	closeNotifyErr error
	// closeNotifySent is true if the Conn attempted to send an
	// alertCloseNotify record.
	closeNotifySent bool

	// clientFinished and serverFinished contain the Finished message sent

	// 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.)
	select {

	if ne, ok := err.(net.Error); ok {
		return ne.Timeout()
	}
	return false
}

// tests that Conn.Read returns (non-zero, io.EOF) instead of
// (non-zero, nil) when a Close (alertCloseNotify) is sitting right
// behind the application data in the buffer.
func TestConnReadNonzeroAndEOF(t *testing.T) {
	// This test is racy: it assumes that after a write to a