A bicycle resembles the motion of running prey and triggers predatory instincts in most dogs unless they're well trained or exceptionally calm. I stop, get off the bike and put the bike between myself and the dog and take a moment to evaluate the situation. I carry pepper spray but have used it only once in six years.
Most chasing dogs are guarding their territory and stop as soon as we pass their invisible boundaries. And most of them get confused when we stop. So they tend to lose interest and leave.
I also run video on every ride, so I have documentation in case the incident escalates. Unfortunately too many untrained and undisciplined dogs are owned by people who are indifferent or incompetent to be responsible dog owners, and tend to react defensively and with hostility. So try to avoid confrontations or escalation.