Changed dir test-data/* to test/data/*

[jsgm]

Created new directory instead test-data/, applying golang-standards best practices.

This will also help organising better any additional examples regarding the database usage.

[ostafen]

Thank you for the PR. Since the folder structure has been changed, each path inside the db_test.go file should be renamed. I think that currently, most of the tests will fail

[jsgm]

Just changed the tests as well