Domain-Driven Design with Golang

Picture this: a customer support agent asks a simple question about an order, and nobody on your team can answer it with confidence. The rule exists somewhere, maybe in three different places, each one slightly different from the others. Nobody remembers which version is correct anymore.

This is what happens when software gets built around tables and frameworks instead of the business itself. Rules drift. Trust erodes. Every new feature becomes a small act of guesswork.

It doesn't have to be this way.

What if every rule your business cares about lived in exactly one place, written in the same words your team already uses to talk about the work? What if adding a new developer to your project meant teaching them the business, not untangling your code?

That's what this book sets out to build with you, one chapter at a time.

• Why database-first thinking quietly costs you later, and what to do instead
• Entities and value objects: modeling identity, immutability, and self-validation in Go
• Aggregates: enforcing invariants through encapsulation, not convention
• Domain services, repositories, and factories, wired together without a DI framework
• Bounded contexts and context mapping: shared kernels, anticorruption layers, and customer-supplier relationships
• Commands, queries, and CQRS for a clean application layer
• Mapping domain models to SQL and NoSQL storage without leaking persistence details into your business logic
• A complete testing strategy: fast unit tests, table-driven tests, and real integration tests
• Refactoring toward deeper insight as your understanding of the business grows
• Deploying, maintaining, and scaling a system built this way

Every chapter builds on real Go code, worked through in detail, with the reasoning behind each decision explained clearly along the way.

This book is for you if you already write Go comfortably and want your code to hold up as your application grows past its first working version. Whether you're maintaining a system where business rules have started to feel unreliable, or you're starting something new and want to get the foundation right from day one, this book meets you where you are.

Somewhere in your codebase, right now, a business rule is hiding in the wrong place.

You can keep working around it. Or you can learn to build software that says, clearly and honestly, what your business actually does; software your team can trust without needing to ask.

Turn the page. Your domain model is waiting to be built right.