FirebaseRealtimeDatabaseCallbackFlow.kt

fun readFirebaseRealtimeDatabaseFlow(): Flow<String> = callbackFlow {
        
        val database = FirebaseDatabase.getInstance("<path of realtime database>")
        val databaseRef = database.reference

        val firebaseDataListeners = object : ValueEventListener {
            override fun onDataChange(dataSnapshot: DataSnapshot) {
                // This method is called once with the initial value and again
                // whenever data at this location is updated.
                val value = dataSnapshot.value
                Log.d(ContentValues.TAG, "Value is: $value")
                trySend(value?.toString().orEmpty())
            }

            override fun onCancelled(error: DatabaseError) {
                // Failed to read value
                Log.w(ContentValues.TAG, "Failed to read value.", error.toException())
            }
        }

        databaseRef.addValueEventListener(firebaseDataListeners)

        awaitClose {
            databaseRef.removeEventListener(firebaseDataListeners)
        }
        
    }