Normally with ASP.NET Core projects, I have access to the IWebHostBuilder creation, upon which I can register services and build configuration, and then I can get into a Startup class where I can inject any of the services or configurations that were registered while building the host. I use this two-stage approach quite often, as I usually need some services available within Startup to finish registering everything else.
Now I'm working on a Generic Host headless app, adding a BackgroundService with AddHostedService<T>. There is no Startup class in this scenario, so it seems all my dependencies have to be registered while creating the HostBuilder. I'm not able to use my normal services because of the lack of the second registration step.
When using the Generic Host/non-HTTP/BackgroundService/AddHostedService approach, how can I get two stages of dependency registration as I do in Web projects?