After changing my launch target to IIS for my ASP.NET Core project, I got the following error from Visual Studio:
With a recent update to Visual Studio 2017(15.3), Microsoft added support for debugging ASP.NET Core applications against IIS. To be able to use you have to modify your existing Visual Studio Installation. So open up the Visual Studio Installer and select the Development time IIS support component which is listed as optional component under the ASP.NET and web development workload.
This will install the ASP.NET Core Module which is a native IIS module required to run ASP.NET Core applications on IIS. Click on Modify to start the installation.
After the installation has completed, restart Visual Studio and try to run your app again.
More information: https://blogs.msdn.microsoft.com/webdev/2017/07/13/development-time-iis-support-for-asp-net-core-applications/