track1 modify network readme.go.md (#15813)

Author: Alancere

specification/network/resource-manager/readme.go.md

@@ -21,6 +21,7 @@ azure-arm: true
 
 ``` yaml $(go) && $(multiapi)
 batch:
+  - tag: package-2021-03
   - tag: package-2021-02
   - tag: package-2020-11
   - tag: package-2020-08
@@ -60,6 +61,15 @@ batch:
   - tag: package-2015-05-preview
 ```
 
+### Tag: package-2021-03 and go
+
+These settings apply only when `--tag=package-2021-03 --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-2021-03' && $(go)
+output-folder: $(go-sdk-folder)/services/$(namespace)/mgmt/2021-03-01/$(namespace)
+```
+
 ### Tag: package-2021-02 and go
 
 These settings apply only when `--tag=package-2021-02 --go` is specified on the command line.