Add gofmt formatting check to CI

.github/workflows/ci.yml

@@ -25,6 +25,13 @@ jobs:
           go-version: ${{ matrix.go-version }}
       - name: Checkout code
         uses: actions/checkout@v3
+      - name: Check Go code formatting
+        run: |
+          if [ "$(gofmt -s -l . | wc -l)" -gt 0 ]; then
+            gofmt -s -l .
+            echo "Please format Go code by running: go fmt ./..."
+            exit 1
+          fi
       - name: Run tests
         run: |
           mkdir -p bin