I am having interest in both Mechanical and computer engineering, what should I do?

My advice to you would be not to change your branch of engineering. Mechanical engineering is an awesome branch and you can learn so much practically. I advice you not to think of job or anything. As you have told that you have interest in Mech. then continue with it and learn well in that field. Coming to the interest in Computer Science, its really normal to get interested in it as that field seems to be fascinating. I think while doing Mech. Engineering side by side learn the various concepts of Computer science which fascinates you and you can do this by learning in various MOOCs like MIT OCW, Codecademy etc. If you really have interest then you can really learn CSE side by side.
By this you will get very good knowledge in both the fields and thus expanding your opportunities. Don’t let others to make you believe that you cannot learn CSE on your own. All the best for your career.