Update github.com/miekg/dns to pick up fix for CVE-2019-19794.

I noticed this was out of date using 'snyk test' on the main repository.

vendor/github.com/miekg/dns/xfr.go

@@ -182,14 +182,17 @@ func (t *Transfer) inIxfr(q *Msg, c chan *Envelope) {
 //
 //	ch := make(chan *dns.Envelope)
 //	tr := new(dns.Transfer)
-//	go tr.Out(w, r, ch)
+//	var wg sync.WaitGroup
+//	go func() {
+//		tr.Out(w, r, ch)
+//		wg.Done()
+//	}()
 //	ch <- &dns.Envelope{RR: []dns.RR{soa, rr1, rr2, rr3, soa}}
 //	close(ch)
-//	w.Hijack()
-//	// w.Close() // Client closes connection
+//	wg.Wait() // wait until everything is written out
+//	w.Close() // close connection
 //
-// The server is responsible for sending the correct sequence of RRs through the
-// channel ch.
+// The server is responsible for sending the correct sequence of RRs through the channel ch.
 func (t *Transfer) Out(w ResponseWriter, q *Msg, ch chan *Envelope) error {
 	for x := range ch {
 		r := new(Msg)
@@ -198,11 +201,14 @@ func (t *Transfer) Out(w ResponseWriter, q *Msg, ch chan *Envelope) error {
 		r.Authoritative = true
 		// assume it fits TODO(miek): fix
 		r.Answer = append(r.Answer, x.RR...)
+		if tsig := q.IsTsig(); tsig != nil && w.TsigStatus() == nil {
+			r.SetTsig(tsig.Hdr.Name, tsig.Algorithm, tsig.Fudge, time.Now().Unix())
+		}
 		if err := w.WriteMsg(r); err != nil {
 			return err
 		}
+		w.TsigTimersOnly(true)
 	}
-	w.TsigTimersOnly(true)
 	return nil
 }