Apply go fix modernizations

mdns.go

@@ -46,8 +46,8 @@ func extractNetaudioChanDevice(s string) string {
 		return ""
 	}
 	name := strings.ReplaceAll(s[:idx], "\\", "")
-	if atIdx := strings.Index(name, "@"); atIdx >= 0 {
-		return name[atIdx+1:]
+	if _, after, ok := strings.Cut(name, "@"); ok {
+		return after
 	}
 	return ""
 }
@@ -235,7 +235,7 @@ func (t *Tendrils) sendMDNSQueries(ifaceName string, conn *net.UDPConn) {
 	dest := &net.UDPAddr{IP: net.IPv4(224, 0, 0, 251), Port: 5353}
 
 	n := len(mdnsServices)
-	for i := 0; i < n; i++ {
+	for i := range n {
 		service := mdnsServices[(i+mdnsQueryOffset)%n]
 		msg := new(dns.Msg)
 		msg.SetQuestion(service, dns.TypePTR)