OAuth2 authentication with an CSRF-Token in Flutter - cookies

Question

I want to authenticate my flutter app to an REST API with the Oauth2 package but the REST API ask the CSRF Token in the request. Here is my code, does someone know how and where I can add this Token ?
I tried to modify the example of code provide by Oauth2 flutter library, but it doesn't work.
void Login() async {
final authorizationEndpoint = Uri.parse(
"http://ipadress:8000/oauth2/authorization/");
final username = "user";
final password = "pass";
final identifier = "DG9GSrfae8gCzWDJU0jbxQC6DAUsTl8dSBMxwPEz";
final secret = await getCsrftoken();
var client = await oauth2.resourceOwnerPasswordGrant(
authorizationEndpoint, username, password,
identifier: identifier, secret: secret,);
var result = await client.read("http://ipadress/api/users/me/");
print(result);
new File("~/.myapp/credentials.json")
.writeAsString(client.credentials.toJson());
}
Future<String> getCsrftoken() async {
var response =
await http.get(Uri.encodeFull('http://ipadress:8000/login/'));
var csrftoken =
response.headers.remove('set-cookie').substring(10, 74); //csrf 64 chars
return csrftoken;
}
$ Forbidden (CSRF cookie not set.): /oauth2/authorization/
$ "POST /oauth2/authorization/ HTTP/1.1" 403 2990