眼镜蛇MarkPersistentFlagRequired不适用于Root

Using spf13/Cobra for cli flag parsing.

root command has a field marked required:

rootCmd.PersistentFlags().StringVarP(&configFilePath, "config", "c","", "REQUIRED: config file")
    rootCmd.MarkPersistentFlagRequired("config")    
    rootCmd.MarkFlagRequired("config")

However, cobra does not raise an error if it's the root command.

If I add a subcommand and add a required field, .MarkFlagRequired raises an error as expected if the argument is not provided on the command line.