Run custom hook when an event is received

[goodnessd]

Hello! I'm trying to connect a virtual user (VU) to my socket.io server that joins a room, waits for a message to be sent from the server to that room, and triggers a custom function on receiving that event.

The server has an external trigger that emits an event (fooEvent), and I want to inject a custom hook for some metric collection.

For example, I'd hope to do something like this:

scenarios:
 - name: new socket.io client listening for event 
       flow:
        - emit: ["join", "room1"]
           response:
             on: fooEvent
             function: myCustomFunction

A version of this question has already been asked here, but I believe my use case it subtly different.

All the examples that use response here seem to be dependent on an emit first, and none of them use functions in ./functions.js in the way that I'm trying to use it.