remove unnecessary metric wrapper

metrics/wrapper/conn.go

@@ -13,7 +13,7 @@ var (
 	errUnsupport = errors.New("unsupported operation")
 )
 
-// ServerConn is a server side Conn with metrics supported.
+// serverConn is a server side Conn with metrics supported.
 type serverConn struct {
 	net.Conn
 	service string

metrics/wrapper/listener.go

@@ -1,6 +1,10 @@
 package wrapper
 
-import "net"
+import (
+	"net"
+
+	"github.com/go-gost/core/metrics"
+)
 
 type listener struct {
 	service string
@@ -19,5 +23,10 @@ func (ln *listener) Accept() (net.Conn, error) {
 	if err != nil {
 		return nil, err
 	}
+
+	// metrics is not enabled
+	if metrics.Global() == metrics.Noop() {
+		return c, nil
+	}
 	return WrapConn(ln.service, c), nil
 }