Introduce standards across golang based projects

We currently have a number golang based projects and a few maintainers cross them.

It would be helpful if we could collect and write some documentation about standards that maintainers in projects like gitlab-workhorse, gitlab-pages, elastic-search-indexer, gitlab-runner enforce.

This will be helpful when enforcing code quality across projects. It would also be helpful to align in what package managers are used cross projects to remove the complexity of switching between different projects.

Mentioning a few maintainers and frequent contributors to start off this discussion: @nick.thomas @jacobvosmaer-gitlab @ayufan @tmaczukin @nolith @zj @SteveAzz

This issue is created in GitLab CE because all our development documentation including database guides are here. We can move to a different project if required.