Many different types of lenses are utilized in street photography. Most commonly used are the 28mm, the 35mm, the 50mm and 85 mm (in my case).
With different focal lengths– you create a different type of image. The wider you go, your images tend to feel much more intimate– as the perspective makes you feel that you are really in the photograph as an active participant, rather than an outside voyeur.
Everyone has their own preference when it comes to focal length. I would say experiment with different focal lengths, and find what suits you the best.
I have experimented with a lot of different focal lengths, and I have found that 85mm suits me quite well (so I have broken the settled rule that street photography is suitable for most 28 mm and 35 mm focal length lenses) although as expressed in the majority of street photographers, 85 mm focal length is limited, can not always cover everything you want to display.
Experiment with different focal lengths, but once you find a focal length that suits you well– I would stay stick with it. It will help you to understand a focal length very well, and know how far or close you have to stand to your subjects to create a certain frame. Not only that, but it will create a visual coherence in your images that are consistent across a project you may pursue.