Return an element from a function (Kotlin)-CodePudding

I want to return an element from the function but I get the error "lateinit property policlinic has not been initialized". By the way, when I try to write to the Toast message, data comes in successfully.

private lateinit var policlinic: String

private fun useranddoctor(): String{
        val collection = Firebase.firestore.collection("users")
        collection.get()
            .addOnSuccessListener { documentSnapshot ->
                for (document in documentSnapshot) {
                    if (document.getString("kullaniciseviyesi") == "1" && document.getString("email") == firebaseAuth.currentUser?.email) {
                        policlinic = document.getString("policlinic")!!
                    }
                }
            }.addOnFailureListener {

            }
        return policlinic
    }

CodePudding user response：

private var policlinic: String? = null

private fun useranddoctor(): String{
        val collection = Firebase.firestore.collection("users")
        collection.get()
            .addOnSuccessListener { documentSnapshot ->
                for (document in documentSnapshot) {
                    if (document.getString("kullaniciseviyesi") == "1" && document.getString("email") == firebaseAuth.currentUser?.email) {
                        policlinic = document.getString("policlinic")!!
                    }
                }
            }.addOnFailureListener {

            }
        return policlinic
    }