Generally speaking you will have 1 go module per repository / project. You could arrange your code how you have it, but that implies 2 modules which is almost certainly not what you want. What you PROBABLY want is something like this:
You certain CAN have a module that references another module you maintain if it makes sense to separate them in that way. And you can also create a workspace if you must have multiple modules in a single project/repo (which as I mentioned is probably not what you want):
Also if you haven’t yet, check this out:
It contains a lot of useful, idiomatic advice on code organization.