URL Shortener API (Go + Fiber + PostgreSQL)

A lightweight URL shortener backend built with Go, Fiber, and PostgreSQL.

This project provides:

• Short URL creation endpoint
• Redirect endpoint for short codes
• Optional expiration support per URL
• Basic click counting on redirects
• Auto-migration for the urls table on startup

Tech Stack

• Go (module-based project)
• Fiber v2 (web framework)
• PostgreSQL
• pgx v5 (PostgreSQL driver)
• godotenv (environment variable loading)

Project Structure

cmd/
  main.go                  # App bootstrap and server startup
internal/
  database/
    database.go            # DB connection setup
    migrate.go             # Schema migration
    query.go               # DB query helpers
  handlers/
    shorten.go             # POST /api/v1/shorten
    redirect.go            # GET /:code
  models/
    requests.go            # Request DTOs
    url.go                 # URL model
  routes/
    routes.go              # Route registration
  utils/
    code.go                # Short code generator

Features

• POST /api/v1/shorten

  • Accepts a target URL and optional expiration time in seconds
  • Generates a random 6-character short code
  • Stores the record in PostgreSQL
  • Returns a full short URL (currently http://localhost:3000/{code})

• GET /:code

  • Looks up short code
  • Rejects missing/expired links
  • Increments click count
  • Redirects to original URL with HTTP 301 Moved Permanently

Prerequisites

• Go (latest stable recommended)
• PostgreSQL (local or remote)
• Git (for version control and GitHub push)

Environment Variables

The app loads environment variables from .env in the project root.

Create a .env file with:

DB_USER=postgres
DB_PASSWORD=your_password
DB_HOST=localhost
DB_PORT=5432
DB_NAME=url_shortner
DB_SSLMODE=disable

Notes:

• DB_SSLMODE=disable is typical for local development.
• For managed databases, use the provider-recommended SSL mode.

Database Setup

1. Create the database:

CREATE DATABASE url_shortner;

2. Start the app. On startup, migration runs automatically and creates table urls if it does not exist.

Current schema created by migration:

CREATE TABLE IF NOT EXISTS urls(
  id SERIAL PRIMARY KEY,
  code TEXT NOT NULL UNIQUE,
  target_url TEXT NOT NULL,
  clicks INT DEFAULT 0,
  created_at TIMESTAMP DEFAULT NOW(),
  expire_at TIMESTAMP NOT NULL
);

Installation & Run

1. Clone repository and enter it:

git clone <your-repo-url>
cd url_shortner

2. Install dependencies:

go mod tidy

3. Configure environment variables in .env.

4. Run the API:

go run cmd/main.go

Server starts on:

• http://localhost:3000

API Reference

Health Check

• GET /health

Response:

{
  "status": "ok",
  "message": "API is healthy"
}

---

Create Short URL

• POST /api/v1/shorten
• Content-Type: application/json

Request body:

{
  "url": "https://example.com/some/long/path",
  "expire_in": 3600,
  "redirect_type" : "301"
}

Fields:

• url (string, required): original URL
• expire_in (int, optional): expiration in seconds from now

Success response example:

{
  "short_url": "http://localhost:3000/Ab3XyZ"
}

Possible errors:

• 400 Bad Request for invalid JSON body
• 400 Bad Request when url is empty
• 500 Internal Server Error for DB insert failure

---

Redirect

• GET /:code

Behavior:

• Finds URL by code
• Rejects if not found (404)
• Rejects if expired (410)
• Increments clicks
• Redirects to target URL (301)

Possible errors:

• 400 Bad Request for missing code
• 404 Not Found if code does not exist
• 410 Gone if URL is expired

Quick cURL Examples

Create short URL:

curl -X POST http://localhost:3000/api/v1/shorten \
  -H "Content-Type: application/json" \
  -d '{"url":"https://golang.org","expire_in":3600}'

Open short URL in browser:

http://localhost:3000/<code>

Check health:

curl http://localhost:3000/health

Notes and Limitations

• Generated short code length is fixed to 6 characters.
• Current code generation uses pseudo-random math/rand.
• No URL ownership/authentication yet.
• No custom alias support yet.
• Base URL is hardcoded (http://localhost:3000) in response.

Troubleshooting

• Error loading .env file

  • Ensure .env exists in project root.

• Unable to connect to Database

  • Verify DB credentials/host/port/db name in .env.
  • Confirm PostgreSQL is running.

• Migration Failed

  • Confirm DB user has permission to create tables.

• API returns 410 URL Expired unexpectedly

  • Check the expire_in value used when creating the link.

Roadmap Ideas

• Add request validation middleware (URL format, expiration bounds)
• Add collision handling/retry for short code uniqueness
• Make base URL configurable via environment variable
• Add unit/integration tests
• Add Docker and docker-compose setup
• Add rate limiting and analytics endpoints

License

Choose a license before public release (for example: MIT).