$ docker run squarescale/contact
Build is done inside a docker image, you don't need anything but docker.
make display the help with available commands.
Run make build to build the executable for linux amd64 arch.
Run make build-image to create a docker image containing the executable.
Run make run-image after to run the built docker image.
A make lint using dockerfile-lint from project atomic and hadoling is available to check is Dockerfile is good.