Feat: multi-arch docker image (#1756)

* Feat: multi-arch docker image

- adapt Dockerfile to support cross-compilation depending on TARGETARCH and TARGETOS variables see https://www.docker.com/blog/faster-multi-platform-builds-dockerfile-cross-compilation-guide/
- set target platforms for docker/build-push-action

* Support running on forks

* Fix ARG format

* Fix docker digest step

* Restrict permissions

* Update action versions

* Set $TARGETPLATFORM explicitly

docker/build-push-action#820 (comment)

---------

Co-authored-by: Norman Gehrsitz <45375059+ngehrsitz@users.noreply.github.com>

.github/workflows/docker.yml

@@ -5,38 +5,44 @@ on:
     tags:
       - 'v*'
 
+permissions:
+  contents: read
+  packages: write
+
 jobs:
   docker-build:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Set up Docker Buildx
         id: buildx
-        uses: docker/setup-buildx-action@v2
+        uses: docker/setup-buildx-action@v3
 
       - name: Login to Github Packages
-        uses: docker/login-action@v2
+        uses: docker/login-action@v3
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Docker meta
         id: meta
-        uses: docker/metadata-action@v4
+        uses: docker/metadata-action@v5
         with:
           images: ghcr.io/swaggo/swag
 
       - name: Build image and push to GitHub Container Registry
-        uses: docker/build-push-action@v2
+        id: docker_build
+        uses: docker/build-push-action@v5
         with:
           context: .
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: |
-            ghcr.io/swaggo/swag:latest
-            ghcr.io/swaggo/swag:${{github.ref_name}}
+            ghcr.io/${{ github.repository }}:latest
+            ghcr.io/${{ github.repository }}:${{github.ref_name}}
           labels: ${{ steps.meta.outputs.labels }}
 
       - name: Image digest

Dockerfile

@@ -1,7 +1,7 @@
 # Dockerfile References: https://docs.docker.com/engine/reference/builder/
 
 # Start from the latest golang base image
-FROM golang:1.21-alpine as builder
+FROM --platform=$BUILDPLATFORM golang:1.21-alpine as builder
 
 # Set the Current Working Directory inside the container
 WORKDIR /app
@@ -15,12 +15,18 @@ RUN go mod download
 # Copy the source from the current directory to the Working Directory inside the container
 COPY . .
 
+# Configure go compiler target platform
+ARG TARGETOS
+ARG TARGETARCH
+ENV GOARCH=$TARGETARCH \
+    GOOS=$TARGETOS
+
 # Build the Go app
 RUN CGO_ENABLED=0 GOOS=linux go build -v -a -installsuffix cgo -o swag cmd/swag/main.go
 
 
 ######## Start a new stage from scratch #######
-FROM scratch
+FROM --platform=$TARGETPLATFORM scratch
 
 WORKDIR /code/