Shrink an Image with a Multi-Stage Build

Labs have no container engine, so nothing is built or started: your files are checked by reading them, the way a reviewer or a CI linter would. docker-compose config (to validate Compose files) and hadolint (a Dockerfile linter) are installed.

The image of the Go service in /home/student/projects/label-printer is 900 MB, because it ships the whole Go toolchain and source code to production.

Task

Rewrite the Dockerfile as a multi-stage build:

• a build stage named build, based on golang:1.23, that compiles a static binary (CGO_ENABLED=0) to /out/label-printer
• a final stage based on gcr.io/distroless/static-debian12 that contains only the binary, copied from the build stage
• the final image runs /label-printer as its entrypoint, as a non-root user (distroless provides nonroot, UID 65532)