Hello Julius,
In fact, documentation is not to well-structured at this point: you need to create config.json, as detailed on the "Using Structured Data with Node.js" page [1], rather than simply to copy it. The right order of things is: create config.json then copy it in accordance with instructions to be found on the "Using Structured Data with Node.js" page [1].
An issue has been created for documentation people to look into, who will modify the tutorial page and make it more explicit and clearer, with the right sequence of actions to be undertaken.