Add multi-platform build support (#8)

Author: dnelen

.github/workflows/build-docker-image.yml

@@ -6,8 +6,11 @@ on:
       - '*'
 
 jobs:
-  docker:
+  build-and-push-image:
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v3
@@ -34,11 +37,12 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Build and Push Docker Image
-        uses: docker/build-push-action@v3
+        uses: docker/build-push-action@v6
         env:
           DOCKER_BUILDKIT: 1
         with:
           context: .
+          platforms: linux/amd64,linux/arm64
           file: docker/Dockerfile
           push: true
           tags: ${{ steps.meta.outputs.tags }}

docker/Dockerfile

@@ -1,14 +1,17 @@
-FROM golang:1.25 AS builder
+FROM --platform=$BUILDPLATFORM golang:1.25 AS builder
+ARG TARGETOS
+ARG TARGETARCH
 WORKDIR /opt/keepup/
-COPY go.mod ./
-COPY go.sum .
-COPY src ./src
+COPY go.mod go.sum ./
+COPY src ./src/
 RUN go mod download
-RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o helm-scraper src/main.go
+RUN CGO_ENABLED=0 \
+    GOOS=$TARGETOS \
+    GOARCH=$TARGETARCH \
+    go build -a -installsuffix cgo -o helm-scraper src/main.go
 
-FROM alpine:latest
+FROM alpine:3
 WORKDIR /opt/keepup/
 COPY --from=builder /opt/keepup/helm-scraper .
 RUN chmod +x /opt/keepup/helm-scraper
-
 ENTRYPOINT ["/opt/keepup/helm-scraper"]