I have problem in build context

[Apyxxx]

Don't use 'BuildContext's across async gaps.
it is showing in select_contacts_repository.dart file :

void selectContact(Contact selectedContact, BuildContext context) async {
try {
var userCollection = await firestore.collection('users').get();
bool isFound = false;

  for (var document in userCollection.docs) {
    var userData = UserModel.fromMap(document.data());
    String selectedPhoneNum = selectedContact.phones[0].number.replaceAll(
      ' ',
      '',
    );
    if (selectedPhoneNum == userData.phoneNumber) {
      isFound = true;
      
      //from here showing error.....
      Navigator.pushNamed( context, MobileChatScreen.routeName,  arguments: {
        
          'name': userData.name,
          'uid': userData.uid,
          'isGroupChat' : userData.groupId,
          'profilePic' : userData.profilePic,
          
        },
      );
    }
  }

i tried adding
if (!mounted) return;
but it didn't work I think I didn't know how to use it

hope I can get some help
and think you for this amazing app!!