If I may ask, what is your goal with collecting feedback of your survey? If it is to just get a general impression of what people think, then I would avoid this. In my experience the large majority of participants don't provide any or very basic feedback(e.g., survey is good/okay/long/short). The remaining offer feedback, but not in a constructive way (e.g., I don't like this survey; X question was stupid).

Instead I would suggest pilot testing with people in person for such general feedback.

If you want specific feedback about a specific question or aspect of the survey, then you may have better luck. I would ask for feedback about that question/aspect as close to the element as possible. For example, if you have a question that you aren't sure participants understand - ask the question, then immediately after, ask them if they understand/or describe the previous question to you.

I hope this helps!