Getting Started with Dependency Injection in ASP.NET Core

I've lately been feeling my way around getting an actual, production-readyASP.NET Core app developed, and one of the features I've really been digging (one of many) is native support for Dependency Injection (DI). DI is huge in modern web apps, so making it the default for ASP.NET Core applications is, IMO, a big step forward for this framework.