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 off-the-shelf injection

As I mentioned in the previous section, by adopting Wire we are hoping to see a significant reduction in the code and complexity in main(). We are also hoping to be able to essentially forget about the instantiation order of the dependencies by leaving the framework to handle it for us.

Adopting Google Wire

The first thing we need to do, however, is to get our house in order. Most, if not all, of the objects we are going to let Wire handle use our *config.Config object, and currently it exists as a global singleton, as shown in the following code:

// App is the application config
var App *Config

// Load returns the config loaded from environment
func init() {
filename, found := os.LookupEnv...