Because the application crashes. For whom saving time on this exception!
And the error code says it throws an exception because it can't find a file in the initial phase. See the Environment Settings section. In my scenario, it worked when I changed the following code
var environment = whb.GetSetting("environment");
to
var environment = "Development";// whb.GetSetting("environment");
Because I have appsettings.development.json but I didn't have appsettings.production.json. Why it can't find any file because it's looking for different thing on right place.