Go training through Gitaly and Runners work

Per #66 (comment 26936877), we'd like to expand the group of people who are comfortable with Golang by having them work on Workhorse, Runner, GitLab Pages, or Gitaly.

Stan's proposal:

1. Tag all the relatively straightforward fixes with "Accepting Merge Requests". For Workhorse: https://gitlab.com/gitlab-org/gitlab-workhorse/issues?label_name%5B%5D=Accepting+Merge+Requests

Then, per person

1. Start with a well-defined, simple task, such as such as gitlab-org/gitlab-workhorse#99 (closed)
2. Point people to online tutorials and join #golang.
3. Pair experienced Go developers with new ones.
4. Solve the task and move onto another one.
5. Rinse and repeat.

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@DouweM @smcgivern @rymai as a next step, does it make sense for you to announce this / solicit or pick volunteers to start learning more Go from your teams? Perhaps just one from each team is enough. @ayufan @jacobvosmaer-gitlab @andrewn can then perhaps either act as mentors or pick mentors? This is a pyramid scheme: when you are done getting trained, you should be the trainer for the next person, etc.