go: Require go 1.19 and fix new gofmt errors
Conform to function commenting requirements of 1.19 go fmt.
How to register an account on GitLab. To prevent spam, new accounts are locked until approved by an admin or the approver bot. You can also file an unlock request to expedite access.
Support: mw:GitLab, how to host a project on GitLab, #wikimedia-gitlab on libera.chat, #GitLab on Phabricator.
Conform to function commenting requirements of 1.19 go fmt.