build(ci): fix linter errcheck errors

.golangci.yml

@@ -37,7 +37,6 @@ linters-settings:
         # Default: false
         strict: false
 
-
 linters:
   disable-all: true
   enable:
@@ -58,4 +57,9 @@ issues:
   # Maximum count of issues with the same text.
   # Set to 0 to disable.
   # Default: 3
-  max-same-issues: 50
+  max-same-issues: 50
+  exclude-rules:
+    # Exclude some linters from running on tests files.
+    - path: _test\.go
+      linters:
+        - errcheck

src/zdns/answers.go

@@ -410,7 +410,7 @@ func makeEDNSAnswer(cAns *dns.OPT) EDNSAnswer {
 				KeyLease: opt.KeyLease,
 			}
 		case *dns.EDNS0_NSID: //OPT 3
-			hexDecoded, err := hex.DecodeString(o.(*dns.EDNS0_NSID).Nsid)
+			hexDecoded, err := hex.DecodeString(opt.Nsid)
 			if err != nil {
 				continue
 			}
@@ -443,15 +443,15 @@ func makeEDNSAnswer(cAns *dns.OPT) EDNSAnswer {
 				Expire: opt.Expire,
 			}
 		case *dns.EDNS0_COOKIE: //OPT 11
-			optRes.Cookie = &Edns0Cookie{Cookie: o.(*dns.EDNS0_COOKIE).Cookie}
+			optRes.Cookie = &Edns0Cookie{Cookie: opt.Cookie}
 		case *dns.EDNS0_TCP_KEEPALIVE: //OPT 11
 			optRes.TCPKeepalive = &Edns0TCPKeepalive{
 				Code:    opt.Code,
 				Timeout: opt.Timeout,
 				Length:  opt.Length, // deprecated, always equal to 0, keeping it here for a better readability
 			}
 		case *dns.EDNS0_PADDING: //OPT 12
-			optRes.Padding = &Edns0Padding{Padding: o.(*dns.EDNS0_PADDING).String()}
+			optRes.Padding = &Edns0Padding{Padding: opt.String()}
 		case *dns.EDNS0_EDE: //OPT 15
 			optRes.EDE = append(optRes.EDE, &Edns0Ede{
 				InfoCode:      opt.InfoCode,

src/zdns/resolver.go

@@ -452,7 +452,13 @@ func (r *Resolver) getConnectionInfo(nameServer *NameServer) (*ConnectionInfo, e
 			if err != nil {
 				return nil, fmt.Errorf("unable to find default IP address to open socket: %w", err)
 			}
-			localAddr = &conn.LocalAddr().(*net.UDPAddr).IP
+
+			localUDPAddr, ok := conn.LocalAddr().(*net.UDPAddr)
+			if !ok {
+				return nil, errors.New("unable to get local address from connection")
+			}
+			localAddr = &localUDPAddr.IP
+
 			// cleanup socket
 			if err = conn.Close(); err != nil {
 				log.Error("unable to close test connection to Google public DNS: ", err)