Add Docker build pipeline

.github/workflows/build.yml

@@ -0,0 +1,33 @@
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to ghcr.io
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ghcr.io/${{ github.repository_owner }}/cloudflare-dns-failover

Dockerfile

@@ -0,0 +1,15 @@
+FROM golang:1.22.1-alpine3.19 AS builder
+
+ENV GOARCH $TARGETARCH
+ENV CGO_ENABLED=0
+
+WORKDIR /build
+COPY *.go go.* ./
+
+RUN go build -buildvcs=false -ldflags="-w -s" -o ./cloudflare-dns-failover
+
+FROM scratch
+
+COPY --from=builder /build/cloudflare-dns-failover /bin/cloudflare-dns-failover
+
+ENTRYPOINT ["/bin/cloudflare-dns-failover"]