Need to work on my listening

I am a very well behaved boy and I listen fairly well to my parents. I have this problem though when I am outside without my leash and I see someone walk by I go after them. I don't want to hurt them I just like making new friends. When my parents tell me "no" or to "stay" I totally ignor them because I am so excited. Any other time I am good with my boundries. Any suggestions to get me to listen when such distractions happen? Please help because mommy is thinking about getting me a shock collar.