Graceful SIGINT killing

Given is a mock process which runs indefinitely and blocks the program. Right now the only way to stop the program is to send a SIGINT (Ctrl-C). Killing a process like that is not graceful, so we want to try to gracefully stop the process first.

Change the program to do the following:

1. On SIGINT try to gracefully stop the process using proc.Stop()
2. If SIGINT is called again, just kill the program (last resort)