How to get a refresh token from an Aqueduct server

The Aqueduct docs say that the server should return a refresh token. It should look like this:

{
  "access_token" : "Abca09zzzza2o2kelmzlli3ijlka",
  "token_type" : "bearer",
  "refresh_token" : "lkmLIAmooa898nm20jannnnnxaww",
  "expire_in" : 3600
}

But this is what the server actually gives:

{
    "access_token": "uArVqRgpGKv98aNJpziSmTQiFaX2Ebrz",
    "token_type": "bearer",
    "expires_in": 86399
}

There is no refresh_token.

Here is what my controller looks like:

class DemoChannel extends ApplicationChannel {
  ManagedContext context;
  AuthServer authServer;

  @override
  Future prepare() async {
    logger.onRecord.listen((rec) => print("$rec ${rec.error ?? ""} ${rec.stackTrace ?? ""}"));

    final config = WordConfig(options.configurationFilePath);
    final dataModel = ManagedDataModel.fromCurrentMirrorSystem();
    final persistentStore = PostgreSQLPersistentStore.fromConnectionInfo(
        config.database.username,
        config.database.password,
        config.database.host,
        config.database.port,
        config.database.databaseName);

    context = ManagedContext(dataModel, persistentStore);

    final authStorage = ManagedAuthDelegate<User>(context);
    authServer = AuthServer(authStorage);
  }

  @override
  Controller get entryPoint {
    final router = Router();

    router
        .route('/register')
        .link(() => RegisterController(context, authServer));

    router
        .route('/auth/token')
        .link(() => AuthController(authServer));

    router
        .route('/words/[:id]')
        .link(() => Authorizer.bearer(authServer))
        .link(() => WordsController(context));

    return router;
  }
}

My AuthController is just the standard one that comes with Aqueduct. I didn't even see any parameters to adjust in the source code.

How do I make the server send back a refresh token?

It sounds like you are authenticating a public OAuth 2 client. By rule, a public client cannot have a refresh token. You must use a confidential client. A client is confidential when it has a secret. Use the —secret option when creating your client.