Importing Go test utility function from subpackages

I have a test file called db/db_test.go and I want to import a NewMock() function from db/google_test/mock.go (mock.go has package name google_test). That works.

If I rename db/google_test/mock.go to db/google/mock_test.go, even if its package name is google_test, then when I compile db_test.go, it cannot find NewMock() (cannot find package ".../db/google_test"), even though I have an import .../db/google_test in db_test.go.

Is there any way to place my mocker into the package db/google with a package name of google_test and have it be found by the db_test.go code?

Can test sub-packages be imported in test packages higher up the directory tree?