savign timestamp flutter firebase code example

Example: flutter firebase timestamp

Future<List<Post>> getAllPost(Post lastFetched, int fetchLimit) async {
    List<Post> _postList = [];
    if (lastFetched == null) {
      _querySnapshot = await Firestore.instance
          .collection("posts")
          .orderBy("liked", descending: true)
          .limit(fetchLimit)
          .getDocuments();
    } else {
      _querySnapshot = await Firestore.instance
          .collection("posts")
          .orderBy("liked", descending: true)
          .startAfterDocument(lastDocument)
          .limit(fetchLimit)
          .getDocuments();
    }
    if (_querySnapshot.documents.length != 0) {
      lastDocument =
          _querySnapshot.documents[_querySnapshot.documents.length - 1];
    }

    for (DocumentSnapshot documentSnapshot in _querySnapshot.documents) {
      Post tekPost = Post.fromMap(documentSnapshot.data);
      _postList.add(tekPost);
    }
    return _postList;
  }