Source in file for case statement

Question

I have a simple code that runs a case statement that will grow over time. I want other users to update the possible cases but I don't want them to update the code. Is it possible to source in the options from a file called optionsfile.txt?

Current sample:

read input
case $input in
option1 )
  echo option1 ;;
option2 )
  echo option2 ;;
esac

Changed to:

read input
case $input in
Source in file here optionsfile.txt
esac

So the contents of the optionsfile.txt will look like this:

option1 )
  echo option1 ;;
option2 )
  echo option2 ;;

Answer 1

So I ended up using a script that gets called if the date time stamp is updated on the optionsfile.txt that makes a function. That function is sourced into the main code.

#!/bin/bash
cat <<Part1
userstuff() {
read input
case $input in
Part1
cat ./optionsfile.txt
cat <<Part2
esac
}
Part2

Thank you.