How to Build a CRUD App with Golang, Gin, and PostgreSQL

This tutorial shows you how to build a simple CRUD (Create, Read, Update, Delete) application using Golang, the Gin framework, and PostgreSQL. You'll learn to manage data stored in a PostgreSQL database.

Table of Contents

1. Introduction
2. Prerequisites
3. Project Structure
4. Project Setup
5. Database and Table Creation
6. Implementing CRUD Handlers
7. API Testing
8. Conclusion

1. Introduction

This guide utilizes Gin, a lightweight Golang web framework, to create API endpoints. The application interacts with a PostgreSQL database via the pgx driver. Basic familiarity with Golang and REST APIs is assumed.

2. Prerequisites

Before starting, ensure you have:

• Golang (version 1.20 or later)
• PostgreSQL (any version)
• Postman (or a similar API testing tool)
• A code editor (e.g., VS Code)

3. Project Structure

Organize your project as follows:

<code>crud-app/
├── main.go            
├── config/
│   └── database.go    
├── controllers/
│   └── item.go        
├── models/
│   └── item.go        
├── routes/
│   └── routes.go      
├── go.mod             
└── go.sum             </code>

4. Project Setup

1. Create the project directory and initialize a Go module:

   <code class="language-bash">mkdir crud-app
   cd crud-app
   go mod init github.com/yourusername/crud-app  // Replace with your GitHub username</code>

2. Install necessary packages:

   <code class="language-bash">go get github.com/gin-gonic/gin
   go get github.com/jackc/pgx/v5</code>

5. Database and Table Creation

1. Create a PostgreSQL database (e.g., crud_app).

2. Connect to the database and create the items table:

   <code class="language-sql">CREATE DATABASE crud_app;
   \c crud_app
   CREATE TABLE items (
       id SERIAL PRIMARY KEY,
       name TEXT NOT NULL,
       description TEXT,
       price NUMERIC(10, 2)
   );</code>

6. Implementing CRUD Handlers

6.1 Database Connection (config/database.go):

<code class="language-go">package config

import (
    "database/sql"
    "fmt"
    "log"

    _ "github.com/jackc/pgx/v5/stdlib"
)

var DB *sql.DB

func ConnectDatabase() {
    // ... (Connection string with your credentials) ...
}</code>

6.2 Model Definition (models/item.go):

<code class="language-go">package models

type Item struct {
    ID          int     `json:"id"`
    Name        string  `json:"name"`
    Description string  `json:"description"`
    Price       float64 `json:"price"`
}</code>

6.3 CRUD Handlers (controllers/item.go): (Example: Create)

<code class="language-go">package controllers

import (
    "crud-app/config"
    "crud-app/models"
    "github.com/gin-gonic/gin"
    "net/http"
)

func CreateItem(c *gin.Context) {
    // ... (Implementation for creating a new item) ...
}</code>

Implement similar functions for reading, updating, and deleting items.

6.4 Route Definitions (routes/routes.go):

<code class="language-go">package routes

import (
    "crud-app/controllers"
    "github.com/gin-gonic/gin"
)

func SetupRoutes(router *gin.Engine) {
    router.POST("/items", controllers.CreateItem)
    // ... (Add routes for other CRUD operations) ...
}</code>

6.5 Main Application (main.go):

<code class="language-go">package main

import (
    "crud-app/config"
    "crud-app/routes"
    "github.com/gin-gonic/gin"
)

func main() {
    config.ConnectDatabase()
    r := gin.Default()
    routes.SetupRoutes(r)
    r.Run(":8080")
}</code>

7. API Testing

Run the application (go run main.go) and test the endpoints using Postman or a similar tool.

8. Conclusion

You've successfully created a basic CRUD application. Remember to fill in the missing CRUD handler implementations and adapt the database connection string to your environment. This foundation can be expanded upon with more advanced features.

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