fix metrics for listener

metrics/wrapper/conn.go

@@ -86,7 +86,7 @@ type packetConn struct {
 }
 
 func WrapPacketConn(service string, pc net.PacketConn) net.PacketConn {
-	if !xmetrics.IsEnabled() {
+	if !xmetrics.IsEnabled() || pc == nil {
 		return pc
 	}
 	return &packetConn{

metrics/wrapper/listener.go

@@ -2,8 +2,6 @@ package wrapper
 
 import (
 	"net"
-
-	xmetrics "github.com/go-gost/x/metrics"
 )
 
 type listener struct {
@@ -12,10 +10,6 @@ type listener struct {
 }
 
 func WrapListener(service string, ln net.Listener) net.Listener {
-	if !xmetrics.IsEnabled() {
-		return ln
-	}
-
 	return &listener{
 		service:  service,
 		Listener: ln,