diff --git a/resolver.go b/resolver.go
index 555def0..689ab19 100644
--- a/resolver.go
+++ b/resolver.go
@@ -23,6 +23,12 @@ func (e ResolvError) Error() string {
 	return errmsg
 }
 
+type RResp struct {
+	msg        *dns.Msg
+	nameserver string
+	rtt        time.Duration
+}
+
 type Resolver struct {
 	servers       []string
 	domain_server *suffixTreeNode
@@ -126,7 +132,7 @@ func (r *Resolver) Lookup(net string, req *dns.Msg) (message *dns.Msg, err error
 
 	qname := req.Question[0].Name
 
-	res := make(chan *dns.Msg, 1)
+	res := make(chan *RResp, 1)
 	var wg sync.WaitGroup
 	L := func(nameserver string) {
 		defer wg.Done()
@@ -145,11 +151,10 @@ func (r *Resolver) Lookup(net string, req *dns.Msg) (message *dns.Msg, err error
 			if r.Rcode == dns.RcodeServerFailure {
 				return
 			}
-		} else {
-			logger.Debug("%s resolv on %s (%s) ttl: %v", UnFqdn(qname), nameserver, net, rtt)
 		}
+		re := &RResp{r, nameserver, rtt}
 		select {
-		case res <- r:
+		case res <- re:
 		default:
 		}
 	}
@@ -163,9 +168,9 @@ func (r *Resolver) Lookup(net string, req *dns.Msg) (message *dns.Msg, err error
 		go L(nameserver)
 		// but exit early, if we have an answer
 		select {
-		case r := <-res:
-			// logger.Debug("%s resolv on %s rtt: %v", UnFqdn(qname), nameserver, rtt)
-			return r, nil
+		case re := <-res:
+			logger.Debug("%s resolv on %s rtt: %v", UnFqdn(qname), re.nameserver, re.rtt)
+			return re.msg, nil
 		case <-ticker.C:
 			continue
 		}
@@ -173,9 +178,9 @@ func (r *Resolver) Lookup(net string, req *dns.Msg) (message *dns.Msg, err error
 	// wait for all the namservers to finish
 	wg.Wait()
 	select {
-	case r := <-res:
-		// logger.Debug("%s resolv on %s rtt: %v", UnFqdn(qname), nameserver, rtt)
-		return r, nil
+	case re := <-res:
+		logger.Debug("%s resolv on %s rtt: %v", UnFqdn(qname), re.nameserver, re.rtt)
+		return re.msg, nil
 	default:
 		return nil, ResolvError{qname, net, nameservers}
 	}
@@ -190,10 +195,12 @@ func (r *Resolver) Nameservers(qname string) []string {
 
 	ns := []string{}
 	if v, found := r.domain_server.search(queryKeys); found {
-		logger.Debug("found upstream: %v", v)
+		logger.Debug("%s be found in domain server list, upstream: %v", qname, v)
 		server := v
-		nameserver := server + ":53"
+		nameserver := net.JoinHostPort(server, "53")
 		ns = append(ns, nameserver)
+		//Ensure query the specific upstream nameserver in async Lookup() function.
+		return ns
 	}
 
 	for _, nameserver := range r.servers {