When developing in .Net Core 2.2 sometimes when there is a configuration error, the debugger fails to attach to the Server process.
Check in the appsettings.json of anything that you added, normally if there is an error, you will see a squigly line on it. - Best practice, code in chunks and see if it breaks anything. I mean write one line of code and check if it passes or no errors happen. Normally this is how development is done when you are learning a new technology on the block.