fix go linter issue

linter_config.json

@@ -0,0 +1,27 @@
+{
+	"Vendor": true,
+	"DisableAll": true,
+	"Enable": [
+		"vet",
+		"safesql",
+		"errcheck",
+		"goconst",
+		"goimports",
+		"varcheck",
+		"gas",
+		"staticcheck",
+		"gosimple",
+		"lll",
+		"unconvert",
+		"misspell",
+		"unconvert"
+		],
+	"Aggregate": true,
+	"WarnUnmatchedNolint": true,
+	"LineLength": 240,
+	"Exclude": [
+		"stun/const.go"
+		],
+	"Deadline": "300s",
+	"Skip": []
+}

stun/discover.go

@@ -126,6 +126,9 @@ func (c *Client) discover(conn net.PacketConn, addr *net.UDPAddr) (NATType, *Hos
 	c.logger.Debugln("Do Test1")
 	c.logger.Debugln("Send To:", changedAddr)
 	caddr, err := net.ResolveUDPAddr("udp", changedAddr.String())
+	if err != nil {
+		c.logger.Debugf("ResolveUDPAddr error: %v", err)
+	}
 	resp, err = c.test1(conn, caddr)
 	if err != nil {
 		return NATError, mappedAddr, err