message: add datamigration tags to Go SDK build
diff: @@ -15,6 +15,8 @@ go:
  batch:
  - tag: package-2017-11-15-preview
  - tag: package-2018-03-31-preview
  + - tag: package-2018-04-19
  + - tag: package-2018-07-15-preview
  ```
  @@ -35,3 +37,21 @@ Please also specify `--go-sdk-folder=<path to the root directory of your azure-s
  ``` yaml $(tag)=='package-2018-03-31-preview' && $(go)
  output-folder: $(go-sdk-folder)/services/preview/$(namespace)/mgmt/2018-03-31-preview/$(namespace)
  ```
  +
  +### Tag: package-2018-04-19 and go
  +
  +These settings apply only when `--tag=package-2018-04-19 --go` is specified on the command line.
  +Please also specify `--go-sdk-folder=<path to the root directory of your azure-sdk-for-go clone>`.
  +
  +``` yaml $(tag)=='package-2018-04-19' && $(go)
  +output-folder: $(go-sdk-folder)/services/$(namespace)/mgmt/2018-04-19/$(namespace)
  +```
  +
  +### Tag: package-2018-07-15-preview and go
  +
  +These settings apply only when `--tag=package-2018-07-15-preview --go` is specified on the command line.
  +Please also specify `--go-sdk-folder=<path to the root directory of your azure-sdk-for-go clone>`.
  +
  +``` yaml $(tag)=='package-2018-07-15-preview' && $(go)
  +output-folder: $(go-sdk-folder)/services/preview/$(namespace)/mgmt/2018-07-15-preview/$(namespace)
  +```
  