What methods can be used to implement dependency injection in code?

Dependency Injection (DI) in Go can be implemented in several ways, considering the language features:

1. Through function or constructor parameters — the most common and straightforward method. Dependencies are explicitly passed when creating an object or calling a function.

type Service struct {
    repo Repository
}

func NewService(r Repository) *Service {
    return &Service{repo: r}
}

2. Using interfaces — allows easy substitution of dependency implementations for testing or extension.

3. DI packages — there are third-party libraries (e.g., Uber Fx, Google Wire) that help automate dependency injection, but their use is not mandatory.

4. Global variables or singletons — a less preferred method due to issues with testability and maintainability.

In Go, explicit injection through parameters is usually preferred, as it enhances code readability and simplicity.