In CI and our development environment we do not rely on the Go environment of the host machine, and instead use Go installed in a container. To simplify things we separate all of Boulder's build dependencies into its own boulder-tools Docker image.

To build boulder-tools images, you'll need a Docker set up to do cross-platform builds (we build for both amd64 and arm64 so developers with Apple silicon can use boulder-tools in their dev environment). On Ubuntu the setup steps are:

docker buildx create --use --name=cross
sudo sudo apt-get install qemu binfmt-support qemu-user-static

After setup, the output of docker buildx ls should contain an entry like:

cross0  unix:///var/run/docker.sock running linux/amd64, linux/386, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/mips64le, linux/mips64, linux/arm/v7, linux/arm/v6

If you see an entry like:

cross0  unix:///var/run/docker.sock stopped

That's probably fine; the instance will be started when you run tag_and_upload.sh (which runs docker buildx build).

Rather than install multiple versions of Go within the same boulder-tools container we maintain separate images for each Go version we support.

When a new Go version is available we perform several steps to integrate it to our workflow:

1. We add it to the GO_VERSIONS array in tag_and_upload.sh.
2. We run the tag_and_upload.sh script to build, tag, and upload a boulder-tools image for each of the GO_VERSIONS
3. We update .github/workflows/boulder-ci.yml, adding the new docker image tag(s) to the BOULDER_TOOLS_TAG section.

After some time when we have spot checked the new Go release and coordinated a staging/prod environment upgrade with the operations team we can remove the old GO_VERSIONS entries, delete their respective build matrix items, and update docker-compose.yml.