api-gateway

A personal project to learn and explore networking and backend programming in Go.

The goal is to build a real, working API gateway from scratch — not to use a framework, not to take shortcuts — and actually understand how things work along the way: how reverse proxying works, how connection pooling is managed, how to handle retries and timeouts correctly, JWT auth, rate limiting, graceful shutdown, etc.

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What this is

• A reverse proxy / API gateway written in Go using only the standard library (plus a few small packages)
• Routes incoming HTTP requests to backend microservices based on path prefix or exact match
• Includes middleware for logging, rate limiting, JWT auth, and CORS
• Health checks for the gateway itself and upstream services
• Configurable per-route timeouts, retries, and auth requirements
• Graceful shutdown on SIGINT/SIGTERM

What I'm learning

• How net/http and httputil.ReverseProxy work under the hood
• Connection pooling and transport configuration
• Middleware chaining patterns
• JWT validation without a big auth library
• Per-IP rate limiting with in-memory state
• Retry logic with exponential backoff
• Graceful shutdown with in-flight request draining
• Structuring a Go project without over-engineering it

Running it

# Local
go build -o api-gateway && ./api-gateway config.yaml

# Docker Compose
docker compose up --build

# Test
bash test.sh

See docs/REFERENCE.md for full configuration, architecture notes, API reference, and deployment details.