message: refine readme.go.md
diff: @@ -33,3 +33,4 @@ Please also specify `--go-sdk-folder=<path to the root directory of your azure-s
  ``` yaml $(tag) == 'package-2020-03-preview' && $(go)
  output-folder: $(go-sdk-folder)/services/preview/$(namespace)/mgmt/2020-03-01-preview/$(namespace)
  +```
  