Add CI workflow

.github/workflows/ci.yml

@@ -0,0 +1,58 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+permissions:
+  contents: read
+
+jobs:
+  build-test:
+    name: Build and Test (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+          - windows-latest
+          - macos-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+          cache: true
+
+      - name: Build
+        run: go build ./...
+
+      - name: Test
+        run: go test ./...
+
+  lint:
+    name: Lint (ubuntu)
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+          cache: true
+
+      - name: Lint
+        uses: golangci/golangci-lint-action@v6
+        with:
+          version: latest
+          args: --timeout=5m