Hard wiring light bulb socket onto whire/black wires -- small shock when touching housing
Go and get a lampholder/socket that is touch safe -- yours is old, and bad, and was never designed to be placed in a position where it could be poked when turned on.  In fact, yours is bad enough that it leaves the screw contact (neutral) exposed instead of having any sort of shell around it.  No wonder you're getting bit by it!