All Golang Imports are relative to the $GOPATH/src. Designing a well built file structure is key to long-term codebase maintainability and fast paced development. Since all imports aren't relative to their own position Golang file structures are different than normal JavaScript or python structures.

In this example I will be using Go-Fiber of which I am a contributing member but this file structure should work with any framework.

1. Structure by Package You can structure your files by each model in the database. This allows to easily find a model's functions by looking at it. A sample project in this layout would look like this.

pkg/
    api/
        auth/
            auth.go
    product/
            product.go
     router/
         router.go
cmd/
    myapp/
        main.go

This file structure has its use cases but there are better ways for general servers.

2. Structure by Function

   You can structure files by their use such as putting handler functions together and middleware together. A file structure of this sort would look similar to this.

database/
    connect.go
    database.go
handlers/
    product.go
    auth.go
middleware/
    authenticated.go
    json.go
    security.go
models/
    user.go
    product.go
router/
    router.go
main.go

This file structure groups by the functional components of each file. It allows for ease of use and access. This is the structure I would recommend for most projects and is what I'm using in my go-fiber project.

Summary

File structures in go are different because of the absolute $GOPATH/src imports. Holding a solid file structure is important in Golang and key to a cleaner codebase. Structuring by function and then by package if a project is large enough is my recommended structure.