add formatter action

.github/workflows/format.yml

@@ -0,0 +1,19 @@
+name: Format
+
+on:
+  pull_request:
+    branches: [main]
+
+jobs:
+  format:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+      with:
+        ref: ${{ github.head_ref }}
+        fetch-depth: 0
+
+    - name: Format code
+      uses: iamnotaturtle/auto-gofmt@v1.0