How to retrive data by a post request

[Caplimbo]

Hello, I am trying to using this library for my course study in university, and in the process I encountered a problem about retriving data by a post request. The format

fun login(name: String, password: String): Int {
        var id = -1
        Okkt.instance.Builder().setUrl("/user/findbyname")
            .setParams(hashMapOf("name" to name)).get(object: CallbackRule<User> {
                override suspend fun onFailed(error: String) {
                    Log.w("login", "name not found")
                }

                override suspend fun onSuccess(entity: User, flag: String) {
                    Log.w("login", "found password on server ${entity.password}")
                    if (password == entity.password) {
                        id = entity.userID  // these lines are useless for id outside
                    }
                    else {
                        id = 0
                        Log.w("login error", "false password")
                    }
                }
            })
        return id
    } 

Here I found that id cannot be assigned the value in the "onSuccess" block. How should I use the data retrived by the post request?