Debug test configuration can't build test binary

[GrantFleming]

Note: I am talking about the vanilla "dap" debug test option that is registered (that I assume is supposed to debug the test file under the cursor) as opposed to the "debug an individual test" option.

Actions Taken

After installing nvim-dap-go (along with nvim-dap), while most debugging options work as expected, the "Debug test" option cannot build the test binary.

Steps to reproduce

1. create a package containing one file and one test file
2. ensure your cursor is in the test file
3. :lua require('dap').continue()
4. select option 6 - "Debug test"

What Happened

Received an error building the test binary due to undefined functions in the test (that are definitely defined in the same package).

Build Error: go test -c -o /Users/grant/Projects/gotest/__debug_bin1012801603 -gcflags all=-N -l /Users/grant/Projects/gotest/pkg/somepackage/somemoretests_test.go
# command-line-arguments [command-line-arguments.test]
pkg/somepackage/somemoretests_test.go:6:13: undefined: UpperIt
pkg/somepackage/somemoretests_test.go:14:13: undefined: UpperIt (exit status 1)

It appears that when you try to test a single file, the required go files are not supplied alongside the test file:

go test somefile_test.go somefile.go

What I Expected to Happen

The tests are built and run successfully.