dart – Graphql Flutter Ferry How to get headers from the response

I’m using Ferry for some queries that I’m making to my GraphQL server. A problem that I’m having is I need to be able to get the access token/refresh token from the cookie/headers. I’m not seeing a way of accessing the headers in the response with ferry.

Current Code:

  @override
  Stream> request(
      OperationRequest request) {
    try {
      Stream> response = _client.request(request);
      response.first.then((requestResponse) {
          final headers = requestResponse // I want to get the headers here somehow but don't see a way.
        
        final authorization = headers?['authorization']?.firstOrNull;
        final cookie = headers?['set-cookie']?.firstOrNull;

        if (authorization != null) {
          _authToken = authorization;
          _securedStorageService.saveAuthToken(authorization);
        }

        if (cookie != null) {
          _refreshToken = cookie;
          _securedStorageService.saveRefreshToken(cookie);

          final maxAge = cookie.split(';').firstWhere(
            (element) => element.contains('Max-Age'),
            orElse: () => '',
          );

          if (maxAge.isNotEmpty) {
            final expirationSeconds = maxAge.split('=').last;
            final expires = DateTime.now().add(Duration(seconds: int.parse(expirationSeconds)));
            _tokenExpired = expires.isBefore(DateTime.now());
            _securedStorageService.saveRefreshTokenExpiration(expires.toIso8601String());
          }
        }

        return requestResponse;
      });
      return response;
    } catch (e) {
      rethrow; // We want to handle errors in the repository layer not here in this lower service layer.
    }
  }

I have looked at the available types on the OperationResponse type but not seeing anyway of accessing the response headers