Update data in Cloud Firestore database using Swift

I updated it like this.

let path1 = ["channels", channel.id!, "thread"].joined(separator: "/")
        let updateReference = db.collection(path1).document(message.id!)
        updateReference.getDocument { (document, err) in
            if let err = err {
                print(err.localizedDescription)
            }
            else {
                document?.reference.updateData([
                    "isRead": true
                    ])
            }
        }