Adding a Backend Module

The internal/app folder

Backend modules are located in the /internal/app folder.

root
|--internal
|  |--app
|     |--[module 1]
|     |--[module 2]
|     |--[...]

Each backend module should have its own folder which should contain the exposed API and all the code for the module's internal workings.

Example

Lets create a simple todo list app called mytodo. Start by initializing a new project.

gofs init github.com/myorg/mytodo mytodo

Now lets create a backend module called list that will contain all the business logic and database logic for the todo list. Lets also say todo lists may not contain more than 20 items because that's just too much to do.

Create the list module folder

Create a folder for the list module.

mytodo
|--internal
|  |--app
|     |--list

Create the list api

Create a new file /internal/app/list/list.go with the List struct and functions for creating a new todo list and adding items to the list. NB: This code is incomplete, you need to add the database code from Persisting data before it will compile.

mytodo
|--internal
|  |--app
|     |--list
|        |--list.go

package list

import (
	"github.com/google/uuid"
)

const MaxItems = 20

type List struct {
	ID    string
	Name  string
	Items []string
}

func NewList(name string) (*List, error) {
	l := &List{
		ID:   uuid.NewString(),
		Name: name,
	}

	// Save list to database
	if err != nil {
		return nil, err
	}

	return l, nil
}

func AddItem(listID string, item string) error {
	l, err := // Retrieve list from the database
	if err != nil {
		return err
	}

	// Check if the list is full
	if len(l.Items) >= MaxItems {
		return fmt.Errorf("Todo list is full")
	}

	l.Items = append(l.Items, item)

	// save to the database
	if err != nil {
		return err
	}

	return nil
}