diff --git a/registry/protocol/protocol.go b/registry/protocol/protocol.go
index 0ffeb3ef7e9e4f043a2a34e174f991b214e4f97a..c8b019bd4cb8d88cb3247660b2cb38c587f09083 100644
--- a/registry/protocol/protocol.go
+++ b/registry/protocol/protocol.go
@@ -45,7 +45,7 @@ import (
 
 var (
 	regProtocol *registryProtocol
-	once sync.Once
+	once        sync.Once
 )
 
 type registryProtocol struct {