When there is a topic or subject in my mind and I would like to speak with my friend about this topic and my friend starts to speak about this topic (automatically) before I speak, I would like to tell him that I was about to speak about the same topic. I was about to say the same speech or the same opinion that he said.. What a coincidence!!
Also, When I have a question in my mind and a person tell me the answer through his speech before listening to my question, I would like to tell him that I was about to ask him about what he already answered.
In my native language, When I speak about this coincidence, It shows that I'm interested in that topic and I love to listen to the Peron who speaks.
Is there a native idiom or expression to tell about this coincidence? How do you say "I was about to tell you about the same topic that you're saying" in a more native way? It is OK if the expression is slang.