Add CI.

.github/workflows/ci.yml

@@ -0,0 +1,42 @@
+name: CI
+
+on: [push]
+
+jobs:
+
+  format:
+    name: Format (gofmt)
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - uses: actions/setup-go@master
+      with:
+        go-version: '1.13'
+    - name: gofmt
+      run: test -z $(gofmt -l .) || (gofmt -d . && exit 1)
+
+  lint:
+    name: Lint (golangci-lint)
+    runs-on: ubuntu-latest
+    needs: [format]
+    steps:
+      - uses: actions/checkout@master
+      - uses: actions/setup-go@master
+        with:
+          go-version: '1.13'
+      - name: golangci-lint
+        run: |
+          curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s v1.22.2
+          cd src
+          ../bin/golangci-lint run -v ./...
+  
+  test:
+    name: Test (go test)
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - uses: actions/setup-go@master
+      with:
+        go-version: '1.13'
+    - name: go test
+      run: go test ./...