Mod: change hessian2 version

go.mod

@@ -2,7 +2,7 @@ module github.com/apache/dubbo-go
 
 require (
 	github.com/Workiva/go-datastructures v1.0.50
-	github.com/apache/dubbo-go-hessian2 v1.2.5-0.20190731020727-1697039810c8
+	github.com/apache/dubbo-go-hessian2 v1.2.4-0.20190807202824-177b9c667283
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dubbogo/getty v1.2.0
 	github.com/dubbogo/gost v1.1.1