Udpate workflow permissions (#219)

To fix code scan alert https://github.com/IBM-Cloud/go-etcd-rules/security/code-scanning/1

Author: kramvan1

.github/workflows/go.yml

@@ -2,6 +2,8 @@
 # For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-go
 
 name: Go
+permissions:
+  contents: read
 
 on:
   push: