Flutter/Dart: save data in different documents in firestore

I am trying to add a data to a firestore with following code.
I select several features such as food, field, date, time, and location. When I press a button Future _addAll function is called and data above are saved into the firestore.

After saving the page moves to main page. The problem starts from here. When I select different data and try to save it to firestore with new documentID, it simply overrides to the previous document unless I refresh the page.

To be specific, when I press the button the data was stored in the document called
-LKV8ZPIAUwk329KqMac. When I selected different data and tried to save to new document, it again was saved in
-LKV8ZPIAUwk329KqMac

Is there a way when I press it saves to a new document each time :) Thank you in advance.

Future _addAll(BuildContext context, List chooseFood, List chooseField, String date, String time, double latitude, double longitude, String text, String uid, String partnerUid) async { _controller.clear(); //clear text message var sendRequestID; //variable to store documentID List connections = new List(); auth.currentUser().then((user) async { //save data to collection('connect') await docRef.setData({ 'createdTime': DateTime.now(), 'foods': chooseFood, 'fields': chooseField, 'meet_date': date, 'meet_time': time, 'latitude': latitude, 'longitude': longitude, 'one_word': text, }).whenComplete(() { sendRequestID = docRef.documentID; print("DB 저장 $sendRequestID"); connections.add(sendRequestID); }).catchError((e) => print(e)); await docRef.collection('connected_users').document('send_request').setData({ //create collection inside a collection 'email': user.email, 'name': user.displayName, 'photoUrl': user.photoUrl }).catchError((e)=>print(e)); }