The preferred authentication method is Basic Authentication. If you try to create, modify or delete a short link, in the browser a popup will appear asking for username and password. Enter just the password you configured. Alternatively you can append a URL query parameter `password` with your configured password.
GoShort is licensed under the MIT license, so you can do basically everything with it, but nevertheless, please contribute your improvements to make GoShort better for everyone. See the LICENSE file.