How can I change so that debugging is not performed on localhost: randomNumber, but on a user domain like my.testsite.com:randomNumber?
I added a domain to the hosts file, and I can manually change the URL when debugging from localhost to my.testsite.com, but can I start VS on my.testsite.com using get-go instead of local?
Yes ... you do this in project options. You can specify your own launch URL as well as a fixed port if you want. The built-in VS server will monitor what you type there, then your hosts file will take care of your mappings.