how to get fcm token

FirebaseApp.initializeApp(this)
    FirebaseMessaging.getInstance().token.addOnCompleteListener { it ->
        if (it.isSuccessful) {
            utils.log("task.isSuccessful = ${it.isSuccessful}")
            token = it.result
            utils.log("token = $token")
        } else {
            utils.log("task.exception = ${it.exception}")
        }
    }