fx

Take a look at the major DI frameworks for Go, Wire [0] and FX [1]. They just plumb the gaps between methods that return types and methods that want them. Although technically they work for concrete types, 99% of the time it's going to be an interface, so that you can substitute a mock for testing. Prior to DI frameworks we used global variables, often initialized in a package's init() method. >The desire to do this reflects a misunderstanding of interfaces. Generally you have a few layers: gRPC/HTTP/Kafka handler, business logic, and database or external service access. Layers are unit tested individually against mocks of the layers below. Because you're going to inject a mock, you can't depend on a concrete type, so you depend on an interface. Often when you're developing you want to know what the concrete implementation of a lower laye