Optimize Docker build for faster multi-platform images.

- Use native Go cross-compilation instead of QEMU emulation.
- Switch to scratch base image for minimal size.
- Add GHA caching for Docker builds.
- Add latest tag for main branch builds.
- Upgrade to Go 1.25.4.

Author: csobrinho

.github/workflows/docker-publish.yml

@@ -4,7 +4,6 @@ on:
   workflow_dispatch:
   push:
     branches: [main]
-    # Publish semver tags as releases.
     tags: ["v*.*.*"]
 
 env:
@@ -22,29 +21,43 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v6
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
+
       - name: Log in to the Container registry
+        if: github.event_name != 'pull_request'
         uses: docker/login-action@v3
         with:
           registry: ${{ env.REGISTRY }}
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
+
       - name: Extract metadata (tags, labels) for Docker
         id: meta
         uses: docker/metadata-action@v5
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=raw,value=latest,enable={{is_default_branch}}
+
       - name: Build and push Docker image
         id: push
         uses: docker/build-push-action@v6
         with:
           context: .
           platforms: linux/amd64,linux/arm64
-          push: true
+          push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
       - name: Generate artifact attestation
+        if: github.event_name != 'pull_request'
         uses: actions/attest-build-provenance@v3
         with:
           subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME}}

Dockerfile

@@ -1,14 +1,18 @@
 # Build stage.
-FROM golang:alpine AS builder
+FROM --platform=$BUILDPLATFORM golang:1.25-alpine AS builder
 WORKDIR /app
+
+# Cache Go modules.
 COPY go.mod go.sum ./
 RUN go mod download
+
+# Build for target platform.
+ARG TARGETOS TARGETARCH
 COPY . .
-RUN go build -o main cmd/supermarket/*
+RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -o main cmd/supermarket/*
 
-# Runner stage.
-FROM alpine:latest AS runner
-RUN apk --no-cache add ca-certificates
-WORKDIR /app
-COPY --from=builder /app/main .
-ENTRYPOINT ["./main"]
+# Runner stage - use scratch for minimal image.
+FROM scratch AS runner
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /app/main /main
+ENTRYPOINT ["/main"]

go.mod

@@ -1,6 +1,6 @@
 module github.com/csobrinho/supermarket-api
 
-go 1.24.3
+go 1.25.4
 
 require (
 	github.com/google/logger v1.1.1