add multi-arch support and CI workflow

.github/workflows/build-container-ghcr.yml

@@ -0,0 +1,45 @@
+name: Build docker containers
+on:
+  push:
+    tags:
+      - "v*"
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    permissions:
+      packages: write
+    env:
+      IMAGE_NAME: ghcr.io/${{ github.repository_owner }}/${{ github.event.repository.name }}
+      VERSION: ${{ github.ref_name }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Login to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      # Build per-arch images
+      - name: Build amd64 image
+        run: |
+          docker build -t ${IMAGE_NAME}:${VERSION}-amd64 -f Dockerfile --build-arg ARCH=amd64 .
+      - name: Build arm64 image
+        run: |
+          docker build -t ${IMAGE_NAME}:${VERSION}-arm64 -f Dockerfile --build-arg ARCH=arm64 .
+      - name: Push per-arch images
+        run: |
+          docker push ${IMAGE_NAME}:${VERSION}-amd64
+          docker push ${IMAGE_NAME}:${VERSION}-arm64
+      # Create multi-arch manifest and push
+      - name: Push multi-arch manifest
+        run: |
+          docker manifest create ${IMAGE_NAME}:${VERSION} \
+            --amend ${IMAGE_NAME}:${VERSION}-amd64 \
+            --amend ${IMAGE_NAME}:${VERSION}-arm64
+          docker manifest push ${IMAGE_NAME}:${VERSION}
+      - name: Tag as latest
+        run: |
+          docker manifest create ${IMAGE_NAME}:latest \
+            --amend ${IMAGE_NAME}:${VERSION}-amd64 \
+            --amend ${IMAGE_NAME}:${VERSION}-arm64
+          docker manifest push ${IMAGE_NAME}:latest

Dockerfile

@@ -1,11 +1,10 @@
-FROM golang:1.24-alpine
-
-WORKDIR /app
-
+FROM golang:1.24-alpine AS build
+ARG ARCH=amd64
+WORKDIR /build
 COPY main.go .
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=${ARCH} go build -o seadex-proxy main.go
 
-RUN go build -o app main.go
-
+FROM scratch
+COPY --from=build /build/seadex-proxy /seadex-proxy
+ENTRYPOINT ["/seadex-proxy"]
 EXPOSE 6778
-
-CMD ["./app"]