private static string SourceDisplayName(IConfigurationSource source)
        {
            if (source is JsonConfigurationSource jsonSource)
            {
                return($"json file: {jsonSource.Path}");
            }

            if (source is CommandLineConfigurationSource)
            {
                return("command line parameters");
            }

            if (source is EnvironmentVariablesConfigurationSource)
            {
                return("environment variables");
            }

            return(source.ToString());
        }