Add gofmt (goimports) Github workflow

.github/workflows/gofmt.yml

@@ -0,0 +1,20 @@
+name: Check code formatting
+on: [push]
+
+jobs:
+  goimports:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Go 1.21
+        uses: actions/setup-go@v4
+        with:
+          go-version: '1.21.x'
+
+      - name: Install goimports
+        run: go install golang.org/x/tools/cmd/goimports@latest
+
+      - name: Check goimports
+        run: if [ "$(goimports -l . | wc -l)" -gt 0 ]; then exit 1; fi