Firestore Database, reading from the databas

App Development
1 
let db = Firestore.firestore()
        db.collection("Users").getDocuments { snapshot, error in
            //check for errors
            if error == nil {
                //no error
                
                if let snapshot = snapshot {
                    //get all docs
                    for doc in snapshot.documents {
                        self.users.append(UserModel(doc.documentID,
                                               doc["Username"] as! String,
                                               doc["Password"] as! String,
                                               doc["Email"] as! String))
                    }
                }
            } else {
                //handle
            }

The snapshot variable doesn’t seem to load all the documents into it. Anyone notice an issue with the code as to why?