Fix/silence a couple of linter warnings

framework/dns/dnssec.go

@@ -283,7 +283,6 @@ func (e ExtResolver) AuthLookupIPAddr(ctx context.Context, host string) (ad bool
 	)
 	if err != nil {
 		// Disregard the error for AAAA lookups.
-		resp = &dns.Msg{}
 		aaaaFailed = true
 		log.DefaultLogger.Error("Network I/O error during AAAA lookup", err, "host", host)
 	} else {

framework/dns/dnssec_test.go

@@ -52,7 +52,7 @@ func (s *IPAddrTestServer) Run() {
 	}
 	s.udpServ.PacketConn = pconn
 	s.udpServ.Handler = s
-	go s.udpServ.ActivateAndServe()
+	go s.udpServ.ActivateAndServe() //nolint:errcheck
 }
 
 func (s *IPAddrTestServer) Close() {
@@ -117,7 +117,9 @@ func (s *IPAddrTestServer) ServeDNS(w dns.ResponseWriter, m *dns.Msg) {
 		}
 	}
 
-	w.WriteMsg(reply)
+	if err := w.WriteMsg(reply); err != nil {
+		panic(err)
+	}
 }
 
 func TestExtResolver_AuthLookupIPAddr(t *testing.T) {

internal/endpoint/smtp/submission.go

@@ -103,7 +103,7 @@ func (s *Session) submissionPrepare(msgMeta *module.MsgMetadata, header *textpro
 		return &exterrors.SMTPError{
 			Code:         554,
 			EnhancedCode: exterrors.EnhancedCode{5, 6, 0},
-			Message:      fmt.Sprintf("Invalid address in From"),
+			Message:      "Invalid address in From",
 			Misc: map[string]interface{}{
 				"modifier": "submission_prepare",
 				"addr":     header.Get("From"),

internal/target/remote/security.go

@@ -399,7 +399,7 @@ func (c *daneDelivery) discoverTLSA(ctx context.Context, mx string) ([]dns.TLSA,
 		return nil, err
 	}
 	if rname == "" {
-		// No A/AAAA records, short-circut discovery instead of doing useless
+		// No A/AAAA records, short-circuit discovery instead of doing useless
 		// queries.
 		return nil, errors.New("no address associated with the host")
 	}