code: func (s *Config) CheckAndSetDefaults() error {
  	if s.Directory == "" {
  		return trace.BadParameter("missing parameter Directory")
  	}
  	if !utils.IsDir(s.Directory) {
  		return trace.BadParameter("path %q does not exist or is not a directory", s.Directory)
  	}
  	return nil
  }
docs: // CheckAndSetDefaults checks and sets default values of file handler config