chore(ci): simplify CI config (#164)

Build against two most recent stable golang releases, to match their
release policy.

.github/workflows/ci.yaml

@@ -0,0 +1,52 @@
+name: ci
+
+on:
+  push:
+    branches: [main] # pushes TO main
+  pull_request:
+    branches: [main] # pull requests AGAINST main
+
+# cancel CI runs when a new commit is pushed to any branch except main
+concurrency:
+  group: "test-${{ github.ref }}"
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        # build against the two latest releases, to match golang's release
+        # policy: https://go.dev/doc/devel/release#policy
+        go-version:
+        - 'stable'
+        - 'oldstable'
+
+    steps:
+    - uses: actions/setup-go@v5
+      with:
+        go-version: ${{matrix.go-version}}
+
+    - uses: actions/checkout@v4
+
+    - name: test
+      run: make testci
+
+    - uses: codecov/codecov-action@v3
+      with:
+        files: ./coverage.out
+      if: ${{ matrix.go-version == 'stable' }}
+
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version: 'stable'
+
+      - uses: golangci/golangci-lint-action@v3
+        with:
+          version: latest

.github/workflows/release.yaml

@@ -15,30 +15,24 @@ jobs:
   docker:
     runs-on: ubuntu-latest
     steps:
-      - name: Check out the repo
-        uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v2
+      - uses: docker/setup-qemu-action@v2
 
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v2
+      - uses: docker/setup-buildx-action@v2
 
-      - name: Login to Docker Hub
-        uses: docker/login-action@v2
+      - uses: docker/login-action@v2
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
-      - name: Extract metadata for Docker
-        id: meta
-        uses: docker/metadata-action@v4
+      - uses: docker/metadata-action@v4
         with:
           images: |
             mccutchen/go-httpbin
+        id: meta
 
-      - name: Build and push
-        uses: docker/build-push-action@v3
+      - uses: docker/build-push-action@v3
         with:
           platforms: linux/amd64,linux/arm64
           push: true