Golang testing using local files

I'm looking for what best practice I should use when it comes to testing with Golang using local files.

By using local files, I mean that in order to test functionality, the application needs some local files, as the application reads from these files frequently.

I'm not sure if I should write temporary files myself just before running the tests using the ioutil package tempdir and tempfile functions, or create a test folder like so;

testing/...test_files_here
main.go
main_test.go

and read from the contents inside

testing/...

Thanks