add support for arm64 docker builds using Buildx+QEMU (#152)

Co-authored-by: flexxxxer <bahx4pc@gmail.com>

.github/workflows/docker-image.yml

@@ -22,9 +22,13 @@ jobs:
         steps:
             - name: Checkout repository
               uses: actions/checkout@v4
+            - name: Set up QEMU
+              uses: docker/setup-qemu-action@v3
+            - name: Set up Docker Buildx
+              uses: docker/setup-buildx-action@v3
             # Uses the `docker/login-action` action to log in to the Container registry registry using the account and password that will publish the packages. Once published, the packages are scoped to the account defined here.
             - name: Log in to the Container registry
-              uses: docker/login-action@65b78e6e13532edd9afa3aa52ac7964289d1a9c1
+              uses: docker/login-action@v3
               with:
                   registry: ${{ env.REGISTRY }}
                   username: ${{ github.actor }}
@@ -32,16 +36,17 @@ jobs:
             # This step uses [docker/metadata-action](https://github.com/docker/metadata-action#about) to extract tags and labels that will be applied to the specified image. The `id` "meta" allows the output of this step to be referenced in a subsequent step. The `images` value provides the base name for the tags and labels.
             - name: Extract metadata (tags, labels) for Docker
               id: meta
-              uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
+              uses: docker/metadata-action@v5
               with:
                   images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
             # This step uses the `docker/build-push-action` action to build the image, based on your repository's `Dockerfile`. If the build succeeds, it pushes the image to GitHub Packages.
             # It uses the `context` parameter to define the build's context as the set of files located in the specified path. For more information, see "[Usage](https://github.com/docker/build-push-action#usage)" in the README of the `docker/build-push-action` repository.
             # It uses the `tags` and `labels` parameters to tag and label the image with the output from the "meta" step.
             - name: Build and push Docker image
-              uses: docker/build-push-action@f2a1d5e99d037542a71f64918e516c093c6f3fc4
+              uses: docker/build-push-action@v6
               with:
                   context: .
                   push: true
+                  platforms: linux/amd64,linux/arm64
                   tags: ${{ steps.meta.outputs.tags }}
                   labels: ${{ steps.meta.outputs.labels }}

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.22.1-alpine3.19 as build
+FROM golang:1.22.1-alpine3.19 AS build
 
 WORKDIR /app
 
@@ -9,7 +9,10 @@ RUN go mod download
 
 COPY . .
 
-ENV CGO_ENABLED=0
+# Architecture and OS are set dynamically (by BuildKit)
+ARG TARGETOS
+ARG TARGETARCH
+ENV CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH
 
 RUN go build -o anonymousoverflow && go build -o healthcheck ./src/healthcheck