chore: validate go mod tidy or pr

.github/workflows/gomod.yml

@@ -0,0 +1,23 @@
+name: Go Mod
+
+on: [pull_request]
+
+jobs:
+  go-mod:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Install Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: 1.15.x
+    - name: Checkout code
+      uses: actions/checkout@v2
+    - name: Check for unused dependencies
+      run: |
+        go mod tidy
+        if [ "$(git status | grep -c "nothing to commit, working tree clean")" == "1" ]; then
+          echo "Nothing to tidy"
+          exit 0
+        fi
+        echo "Go mod tidy is needed"
+        exit 1