As I thought you are not building an addon. You are just putting some lua source code for a LAM in your file and that's all
Please read the links that Ayantir provided and see how an addon must be build in the addon's lua file.
Especially the event like EVENT_ON_ADDON_LOADED etc.
The lua interpreter is reading your source code from the top of the fie downwards to the bottom so be sure to put your variables and functions etc. in the correct order, so that "called variables/functions" further down in your code will be declared above the code where they are called.