code: func AddrsFactory(factory config.AddrsFactory) Option {
  	return func(cfg *Config) error {
  		if cfg.AddrsFactory != nil {
  			return fmt.Errorf("cannot specify multiple address factories")
  		}
  		cfg.AddrsFactory = factory
  		return nil
  	}
  }
docs: // AddrsFactory configures libp2p to use the given address factory.