Document / Improve - Go monorepo

[felickz]

Today Go does not support a paths / paths-ignore based setup with CodeQL (until it supports build-mode: none).

Document a sample of how to best work with this action in a Golang monorepo. Identify improvements to this action/product!

[aegilops]

As long as Go ignores the paths/paths-ignore then having a sparse checkout might be enough for autobuild to function OK?

If not (I'm not sure how it works with nested folders?) for now you'll need to go down the manual build mode approach, and trigger Go with a manual build command.

We can explore how to better support examples such as a wholly Go-based monorepo and a wholly C# monorepo, to be able to get a more completely automatic default that works in those cases.