**Realtime Chat Server (Tutorial → Full‑Featured Implementation)** – A production‑ready Go backend that provides real‑time, room‑based chat with multiple adapters (HTML + Gin, REST, gRPC).  

- **Goal** – Turn a step‑by‑step tutorial into a complete, extensible chat service that can handle thousands of simultaneous messages with low latency.  
- **Broadcast layer** – Defined a `Broadcaster` interface (`Register`, `Unregister`, `Close`, `Submit`). Implemented a thread‑safe broadcaster using channels (`input`, `reg`, `unreg`, `outputs`) and a dedicated goroutine that selects over these channels, guaranteeing race‑free message distribution.  
- **Room manager** – Created a `Manager` interface for opening/closing listeners, submitting messages, and deleting rooms. Each room gets its own `Broadcaster`; the manager coordinates actions through buffered channels (`open`, `close`, `delete`, `messages`).  
- **Singleton pattern** – Exposed the manager via `GetRoomManager()`, ensuring a single shared instance across the whole application and running its `run()` loop in the background.  
- **Adapters**  
  - **HTML + Gin adapter** – Renders a simple HTML template, registers routes for creating rooms, posting messages, deleting rooms, and streaming messages via Server‑Sent Events (SSE).  
  - **REST adapter (implemented)** – Provides `GET /stream/:roomId` (SSE) and `POST /submit` endpoints for clients that prefer a pure JSON API.  
  - **gRPC adapter (optional)** – Structured for future extension, exposing the same `Submit` and `Stream` RPCs.  
- **Concurrency model** – Pure Go channels and goroutines enable thousands of messages per second while keeping registration/unregistration race‑free and guaranteeing clean shutdowns (closed channels prevent panics).  
- **Startup** – A single `main.go` wires everything together: initializes the singleton manager, creates the Gin HTML adapter, registers all routes, and launches the server on port 8080 (`router.Run(":8080")`).  
- **Technologies** – Go 1.20, Gin‑Gonic, HTML templates, Server‑Sent Events, gRPC (planned), channels & goroutines, singleton pattern, RESTful design.  
- **Result** – A fully functional, production‑grade real‑time chat backend that showcases best practices for Go concurrency, clean architecture, and multi‑adapter exposure, ready to be extended with additional front‑ends or scaling layers.