Add Actions (#2)

.github/workflows/go.yml

@@ -0,0 +1,15 @@
+name: Build
+on: [push]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: '1.21'
+      - name: Build
+        run: go build
+      - name: Format
+        run: test -z $(gofmt -l .) || (gofmt -d . && exit 1)