add GitHub Actions config

.github/workflows/push.yml

@@ -0,0 +1,30 @@
+name: Push
+
+on:
+  push:
+    branches: [ master ]
+
+jobs:
+
+  build:
+    name: CI
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Set up Go 1.x
+      uses: actions/setup-go@v2
+      with:
+        # Run on the latest minor release of Go 1.17:
+        go-version: ^1.17
+      id: go
+
+    - name: Check out code into the Go module directory
+      uses: actions/checkout@v2
+
+    - name: Ensure all files were formatted as per gofmt
+      run: |
+        [ "$(gofmt -l $(find . -name '*.go') 2>&1)" = "" ]
+
+    - name: Build packages
+      run: |
+        go install -v ./...