catch SIGINT signal

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**Is your feature request related to a problem? Please describe.**
It would be nice if Drogon would catch the SIGINT and allowed me to run a subroutine.

**Describe the solution you'd like**
catch SIGINT and end program without warnings.

**Describe alternatives you've considered**
I am not sure how to do this in c but in a shell script I would run something like trap on SIGINT.

**Additional context**