Get Firebase Document Snapshot to a Map

I Have to use Map the Snapshot as this method

     Stream<List<writeTime>> readDataStream() {
        final monthData = dateTimeNow('yyyyMMdd');
        print(monthData);
        final path = APIPath.rdatapath(user);
        final reference = FirebaseFirestore.instance
            .collection(path);
        final snapshots = reference.snapshots();
        return snapshots.map((snapshot) => snapshot.docs
            .map((snapshot) => writeTime.fromMap(snapshot.data()))
            .toList());
      }

But Recently I have to Get a Specific Document and I tried this code

    Stream<List<writeTime>> readDataStream() {
        final monthData = dateTimeNow('yyyyMMdd');
        print(monthData);
        final path = APIPath.rdatapath(user);
        final reference =
            FirebaseFirestore.instance.collection(path).doc(monthData);
        final snapshots = reference.snapshots();
        return snapshots.map((snapshot) => snapshot.docs
            .map((snapshot) => writeTime.fromMap(snapshot.data()))
            .toList());
      }

But I have a error in here

 return snapshots.map((snapshot) => snapshot.**docs**
            .map((snapshot) => writeTime.fromMap(snapshot.data()))
            .toList());

And the error is

The getter 'docs' isn't defined for the type 'DocumentSnapshot<Map<String, dynamic>>'.
Try importing the library that defines 'docs', correcting the name to the name of an existing getter, or defining a getter or field named 'docs'.

And I used This map to get data

    factory writeTime.fromMap(Map<String, dynamic> data) {
        if (data == null) {
          throw AssertionError('data must not be null');
        }
        final int thour = data['thour'];
        final int tmin = data["tmin"];
        final int chour = data['chour'];
        final int cmin = data["cmin"];
        return writeTime(thour: thour, tmin: tmin, chour: chour, cmin: cmin);
      }

How I fix this?