Merge pull request #6 from apache/master

feat: check domain empty string (apache#1130)

primitive/nsresolver.go

@@ -99,7 +99,7 @@ type HttpResolver struct {
 
 func NewHttpResolver(instance string, domain ...string) *HttpResolver {
 	d := DEFAULT_NAMESRV_ADDR
-	if len(domain) > 0 {
+	if len(domain) > 0 && domain[0] != "" {
 		d = domain[0]
 	}
 	client := http.Client{Timeout: 10 * time.Second}