Main applications for this project.
The directory name for each application should match the name of the executable you want to have (e.g., /cmd/myapp).
Don't put a lot of code in the application directory. If you think the code can be imported and used in other projects, then it should live in the /pkg directory. If the code is not reusable or if you don't want others to reuse it, put that code in the /internal directory. You'll be surprised what others will do, so be explicit about your intentions!
It's common to have a small main function that imports and invokes the code from the /internal and /pkg directories and nothing else.
See the /cmd directory for examples.
Design and user documents (in addition to your godoc generated documentation).