automatically build a docker container image for the room hub

.github/workflows/docker.yml

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+name: Publish Docker image
+
+on:
+  push:
+
+jobs:
+  push_to_registries:
+    name: Push Docker image to multiple registries
+    runs-on: ubuntu-latest
+    permissions:
+      packages: write
+      contents: read
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v4
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository }}
+
+      - name: Build and push Docker images
+        uses: docker/build-push-action@v5
+        with:
+          context: ./room-hub/
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}

room-hub/Dockerfile

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+FROM golang:1.21-alpine as builder
+
+WORKDIR /proj
+
+COPY go.mod ./
+COPY go.sum ./
+RUN go mod download
+
+COPY *.go ./
+
+RUN go build -o bbb-room-hub
+
+FROM scratch
+
+COPY --from=builder /proj/bbb-room-hub /bbb-room-hub
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+
+EXPOSE 8080
+
+CMD [ "/bbb-room-hub" ]