improve: rDNS 解析等待时间过长

cmd/cmd.go

@@ -56,6 +56,7 @@ func Excute() {
 		// In case of error print error and print usage
 		// This can also be done by passing -h or --help flags
 		fmt.Print(parser.Usage(err))
+		return
 	}
 
 	if *ver {
@@ -65,11 +66,6 @@ func Excute() {
 
 	domain := *str
 
-	if domain == "" {
-		fmt.Print(parser.Usage(err))
-		return
-	}
-
 	if *fast_trace {
 		fastTrace.FastTest(*tcp, *output)
 		if *output {
@@ -79,6 +75,11 @@ func Excute() {
 		os.Exit(0)
 	}
 
+	if domain == "" {
+		fmt.Print(parser.Usage(err))
+		return
+	}
+
 	capabilities_check()
 	// return
 

trace/trace.go

@@ -116,10 +116,25 @@ type Hop struct {
 }
 
 func (h *Hop) fetchIPData(c Config) (err error) {
+	timeout := time.Millisecond * 800
 	if c.RDns && h.Hostname == "" {
-		ptr, err := net.LookupAddr(h.Address.String())
-		if err == nil && len(ptr) > 0 {
-			h.Hostname = ptr[0]
+		result := make(chan []string)
+		go func() {
+			r, err := net.LookupAddr(h.Address.String())
+			if err != nil {
+				result <- nil
+			} else {
+				result <- r
+			}
+		}()
+		select {
+		case ptr := <-result:
+			// process result
+			if err == nil && len(ptr) > 0 {
+				h.Hostname = ptr[0]
+			}
+		case <-time.After(timeout):
+			// handle timeout
 		}
 	}
 	if c.IPGeoSource != nil && h.Geo == nil {