code: func (cfg *Config) Apply(opts ...Option) error {
  	for _, opt := range opts {
  		if opt == nil {
  			continue
  		}
  		if err := opt(cfg); err != nil {
  			return err
  		}
  	}
  	return nil
  }
docs: // Apply applies the given options to the config, returning the first error
  // encountered (if any).