It's super useful to be able to build go binaries in a CI system. It provides the Go toolchain in a container so that you can just use it as a mini-executor. For instance, in Jenkins you can hook up the Jenkins master to a Kubernetes cluster and run your CI in a docker container. The Go docker container is great for this. I can run `go test ...` etc.

Also, when building a container with a Go binary, it's a great base to build from. You can use Docker Multistage Builds[1] to build your binary in the Go container, then copy it out into a minimal container all in the same Dockerfile.

[1]: https://docs.docker.com/develop/develop-images/multistage-bu...