Our latest project at work involved another Go API and in the effort of easing our debugging and issue tracking I'm used to inject the app version into the logs.
It helps a lot monitoring, especially when rolling out a new version (canary, 50% traffic deployment, etc.).
Pre-2018, I hardcoded the version in an app constant which I would increment as part of my release process. It's easy, quick but the only issue is to not forget about it because you may lose versioning syncing over time.
Plus, considering this to be done before each new release, this adds