code: func (bto *BootstrapTokenOptions) AddGroupsFlag(fs *pflag.FlagSet) {
  	fs.StringSliceVar(
  		&bto.Groups, TokenGroups, bto.Groups,
  		fmt.Sprintf("Extra groups that this token will authenticate as when used for authentication. Must match %q", bootstrapapi.BootstrapGroupPattern),
  	)
  }
docs: // AddGroupsFlag adds the --groups flag to the given flagset