Hello! I also am just learning to script, so I’m afraid I can’t help you more than this, but I see one and a half problems:
You have to return the string if you want it to be called and
You have to name the script the same things as you call it. As far as I know the function name has to correspond to the filename, so if the filename matches than you can ignore this point, but as you make more scripts it may be helpful to have consistent naming.
Changing your script to the following should give you your expected results.
function my_function (msg) {
return "Message from my script:" + msg;
} module.exports = my_function