To answer this question, you need to know what the interviewer want to listen. They want to know if you have enough self-awareness to know what you are not good at, at the same time they would like to know what you are going to do about it.
In short, you'd better give a genuine answer of your weakness and tell how you have been working to improve it. It would be great to give a story/example of the effort you have been doing to improve it.
If you have enough time you can go through this video:
One have to understand what the interviewer want to listen before answering this question. So better made the answer stay in the context of your work related goals and direction in the next few years.
Extract from the video below: "An interviewer doesn’t want to hear that you have no goals, that you have unrealistic expectations or that you’re trying to take his job. Try this, instead, talk about some goals that you have over the next few years and how this job is a step in the right direction to accomplish those goals."
Here is a short video to help you understand better if you have the time to watch.
