Design Principles of Software: A Real-World Notification System in Go

Short summary

This tutorial demonstrates how four classic design principles—Single Responsibility, Dependency Inversion, Open/Closed, and Composition—transform a fragile notification module into one that's easy to test and extend. Using a real-world Go example of a multi-channel notification system (email, SMS, WhatsApp), the author shows how each principle eliminates coupling, enables testing, and makes adding new channels trivial. The resulting architecture composes simple, testable components rather than inheriting from brittle base classes.

• •Demonstrates how SRP, DIP, OCP, and Composition principles improve code testability and changeability
• •Real Go code example: building a multi-channel notification system that grows to support email, SMS, WhatsApp
• •Shows how dependency injection and interface-based design eliminate coupling and enable testing without external services

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