Don't know much about middleware? Maybe you don't have to.

I have been to a few .NET Core talks now that exposition middleware, how it works at its most minimum and then progressively how you build rungs on your ladder until you have functioning MVC endpoints to interface with in much the same way René Descartes starts with the "I think therefore I am" cogito and then works his way up to the Catholic Church's worldview in building on top of his own building blocks. Or, then again, maybe it's nothing like that and I'm just giving a goofy analogy. Anyhow... who cares? You really won't have to think about this all that much. When you make a new project in Visual Studio 2017 and pick "ASP.NET Core Web Application (.NET Core)" you will then get three options in a second step:

1. Empty
2. Web API
3. Web Application

I guess you could pick the Empty option and then build up your stuff, but why would you? If you pick Web API you'll start out with a functioning app with a Controller and you may always just click on the Controllers folder and pick: Add > Controller...

Just as a Catholic is unlikely to go about his day thinking of the distinction between Descartes' divide been the phenomenal (what we may know for sure, example: cogito) and the noumenal (what is unprovable) with regards to whether or not there is a God or whether or not belief requires faith... or was that Immanuel Kant who came up with this distinction? I digress. You mostly don't need to think about the middleware. The one exception is that you need to be able to turn on CORS as suggested here.