Kasir API

REST API for a Point-of-Sale (POS) system built with Go. Manages products and categories with PostgreSQL database.

Tech Stack

Component	Technology
Language	Go 1.25.6
Framework	Standard library net/http
Database	PostgreSQL
Config	Viper
Documentation	Swagger (swaggo/swag)

Features

• CRUD operations for Products and Categories
• Product-Category relationship
• Health check endpoint with database connectivity check
• Swagger UI documentation
• Docker support with multi-stage build

Quick Start

Prerequisites

• Go 1.25+
• PostgreSQL
• Docker & Docker Compose (optional)

Local Development

1. Clone the repository

   git clone <repository-url>
   cd kasir-api

2. Configure environment

   cp .env.example .env
   # Edit .env with your database credentials

3. Setup database

   # Connect to PostgreSQL and run the schema (see Database Schema section)
   psql -U postgres -d kasir -f schema.sql

4. Run the application

   make dev
   # or
   go run ./cmd/api

5. Access the API

   • API: http://localhost:8080/api/products
   • Health: http://localhost:8080/health
   • Swagger UI: http://localhost:8080/swagger/

Using Docker

# Build the image
make build

# Start with docker-compose
make run

# View logs
make logs

# Stop
make stop

API Endpoints

Health

Method	Endpoint	Description
GET	/health	Health check (server + database)

Products

Method	Endpoint	Description
GET	/api/products	List all products
POST	/api/products	Create a new product
GET	/api/products/{id}	Get product by ID
PUT	/api/products/{id}	Update product
DELETE	/api/products/{id}	Delete product

Categories

Method	Endpoint	Description
GET	/api/categories	List all categories
POST	/api/categories	Create a new category
GET	/api/categories/{id}	Get category by ID
PUT	/api/categories/{id}	Update category
DELETE	/api/categories/{id}	Delete category

Documentation

Method	Endpoint	Description
GET	/swagger/	Swagger UI

Environment Variables

Variable	Description	Example
PORT	Server port	8080
DB_CONN	PostgreSQL connection string	postgres://user:pass@localhost:5432/kasir?sslmode=disable

Development Commands

Command	Description
make dev	Run application locally
make swagger	Generate Swagger documentation
make build	Build Docker image
make run	Start with docker-compose
make stop	Stop containers
make logs	View container logs
make clean	Remove containers and images
go test ./...	Run all tests

Project Structure

kasir-api/
├── cmd/
│   └── api/
│       └── main.go           # Application entry point
├── internal/
│   ├── apperrors/            # Custom error definitions
│   ├── config/               # Configuration loading
│   ├── database/             # Database connection
│   ├── domain/               # Domain models (Product, Category)
│   ├── handler/              # HTTP handlers
│   ├── repository/           # Data access layer
│   ├── router/               # HTTP routing
│   └── service/              # Business logic layer
├── docs/                     # Generated Swagger documentation
├── .env.example              # Environment variables template
├── Dockerfile                # Multi-stage Docker build
├── docker-compose.yml        # Docker Compose configuration
├── Makefile                  # Development commands
└── go.mod                    # Go module definition

Architecture

HTTP Request
     │
     ▼
┌─────────┐    ┌─────────┐    ┌────────────┐    ┌──────────┐
│ Handler │───▶│ Service │───▶│ Repository │───▶│ Database │
└─────────┘    └─────────┘    └────────────┘    └──────────┘
     │
     ▼
HTTP Response

• Handler: HTTP layer, request/response handling, validation
• Service: Business logic, data orchestration
• Repository: Data access, SQL queries
• Database: PostgreSQL storage

Database Schema

-- Create categories table
CREATE TABLE categories (
    id SERIAL PRIMARY KEY,
    name VARCHAR(255) NOT NULL,
    description TEXT
);

-- Create products table
CREATE TABLE products (
    id SERIAL PRIMARY KEY,
    name VARCHAR(255) NOT NULL,
    price INTEGER NOT NULL,
    stock INTEGER NOT NULL DEFAULT 0,
    category_id INTEGER NOT NULL REFERENCES categories(id)
);

-- Create index for faster product lookups by category
CREATE INDEX idx_products_category_id ON products(category_id);

API Response Format

All API responses follow a consistent format:

Success Response

{
  "success": true,
  "data": {
    "id": 1,
    "name": "Indomie Goreng",
    "price": 3500,
    "stock": 100,
    "category_id": 1,
    "category": {
      "id": 1,
      "name": "Makanan Ringan",
      "description": "Kategori untuk makanan ringan"
    }
  }
}

Error Response

{
  "success": false,
  "error": "Product not found"
}

Health Check Response

{
  "success": true,
  "data": {
    "status": "healthy",
    "database": "connected"
  }
}

Example Requests

Create a Category

curl -X POST http://localhost:8080/api/categories \
  -H "Content-Type: application/json" \
  -d '{"name": "Makanan Ringan", "description": "Snacks and light food"}'

Create a Product

curl -X POST http://localhost:8080/api/products \
  -H "Content-Type: application/json" \
  -d '{"name": "Indomie Goreng", "price": 3500, "stock": 100, "category_id": 1}'

Get All Products

curl http://localhost:8080/api/products

Health Check

curl http://localhost:8080/health