Lua Error?

I'm starting to get into lua coding and I was making a hack menu when something went wrong and got this error

[ERROR] lua/kashackmenu.lua:2: attempt to index global 'vgui' (a nil value)
1. unknown - lua/kashackmenu.lua:2

Does any one know whats wrong ? Ill give you the code if you want

---------- Post added at 12:11 AM ---------- Previous post was at 12:07 AM ----------

Wow none of my scripts are working, ill try restart gmod and see if that works -_-

---------- Post added at 12:17 AM ---------- Previous post was at 12:11 AM ----------

Got it guys doesn't matter lol...

What was wrong? Im getting this with all my scripts now :/