Book Image

Hands-On Dependency Injection in Go

By : Corey Scott
Book Image

Hands-On Dependency Injection in Go

By: Corey Scott

Overview of this book

Hands-On Dependency Injection in Go takes you on a journey, teaching you about refactoring existing code to adopt dependency injection (DI) using various methods available in Go. Of the six methods introduced in this book, some are conventional, such as constructor or method injection, and some unconventional, such as just-in-time or config injection. Each method is explained in detail, focusing on their strengths and weaknesses, and is followed with a step-by-step example of how to apply it. With plenty of examples, you will learn how to leverage DI to transform code into something simple and flexible. You will also discover how to generate and leverage the dependency graph to spot and eliminate issues. Throughout the book, you will learn to leverage DI in combination with test stubs and mocks to test otherwise tricky or impossible scenarios. Hands-On Dependency Injection in Go takes a pragmatic approach and focuses heavily on the code, user experience, and how to achieve long-term benefits through incremental changes. By the end of this book, you will have produced clean code that’s easy to test.
Table of Contents (15 chapters)

Applying config injection

Previously, I mentioned there were a couple of issues that I really wanted us to fix with our ACME registration service. In this section, we are going to use config injection to deal with two of them.

The first is the fact that many of our packages depend on the config and logging packages, and other than being a substantial single responsibility principle violation, this coupling is likely to cause circular dependency problems.

The second is our inability to test our calls to the exchange rate without actually calling the upstream service. So far, we have avoided adding any tests to this package for fear that our tests would then be affected (in terms of speed and stability) by that service.

First, let's examine where we are. Our dependency graph currently looks as shown in the following diagram:

As you can see, we have four packages (data...