review incubator-shenyu-client-golang #5 pr

[Lisandro]

Dear community:

 The  incubator-shenyu-client-golang  has new  pr,please review the code.Here 
is this pr main function:1.Add default handle logic.2.Refactor 
shenyu_admin_client.go.Here is link   
https://github.com/apache/incubator-shenyu-client-golang/pull/5/files