1 - api.go:- This file starts the API server. All your set up logic should be in this file.
2 - services:- This folder contains all the business logic of your application. There should be a file for each type of control. e.g. User service should go into Users.go.
3 - Models:- All the database models should go into the models folder. Again you should write each model into its own file. e.g. User model in UserModel.go.
4 - Routes:- All your routing-related logic should go into this folder. Again divide this logic into multiple files based on functionality.