Not sure if I can add a pointer to help you out Gustavo, but you could use http://localhost as a redirect url if you don’t have a server running he code, then on your browser go o that whole url that will look like this:
https://id.twitch.tv/oauth2/authorize?client_id=<your client id>&redirect_uri=http://localhost&response_type=code&scope=<scopes you need>
When you go to that url from the browser, the url will then contain a code=sdkjff9k032kedfm, then you can use that code to get your oauth token.
Hope this helps