nholisz/roblox-oauth ? reverse-engineered prompt

Build me a Go project that implements Roblox OAuth from scratch.

I want it to handle the full sign in flow, exchange the callback code for tokens, and make it easy to use in a small app or service. Include a simple example showing how to configure it with environment variables and run it locally, and make sure the code is clean and easy to follow.

If anything in the Roblox auth docs has changed, look up the current details online and use the right endpoints and parameters.