Its not a good idea to ask users about features because users are not good at identifying the next features of your product. Instead the questions should be

1) What is the hardest part [about doing this thing]? (Identifies the pain-point of customer)

2) Tell me about the last time you encountered this problem? (Identifies the context of user's problem)

3) Why was that hard? (Identifies the specifics of the problem)

4) What have you done to solve this problem? (Identifies if user is already exploring the potential solution to that problem)

5)What dont you love about the solution that you have tried? (This is the exact question about the features but just in more efficient way)

All of the above questions are summary from YC partner Eric Migicovsky's youtube video on "How to Talk to Users". Its a great informative video.