How to capture an attribute from a random JSON index in serverless artillery

In Artillery, how can I capture the attribute of a random index in a JSON array returned from a GET, so my subsequent POSTs are evenly distributed across the resources?

https://artillery.io/docs/http-reference/#extracting-and-reusing-parts-of-a-response-request-chaining

I'm using serverless artillery to run a load test, which under the hood uses artillery.io .

A lot of my scenarios look like this:

      -
        get:
          url: "/resource"
          capture:
            json: "$[0].id"
            as: "resource_id"
      -
        post:
          url: "/resource/{{ resource_id }}/subresource"
          json:
            body: "Example"

Get a list of resources, and then POST to one of those resources.

As you can see, I am using capture to capture an ID from the JSON response. My problem is that it is always getting the id from the first index of the array.

This will mean in my load test I end up absolutely battering one single resource rather than hitting them evenly which will be a more likely scenario.

I would like to be able to do something like:

capture:
  json: "$[RANDOM].id
  as: "resource_id"

but I have been unable to find anything in the JSONPath definition that would allow me to do so.

Define setResourceId function in custom JS code and to tell Artillery to load your custom code, set config.processor to the JS file path:

processor: "./custom-code.js"

   - get:
      url: "/resource"
      capture:
        json: "$"
        as: "resources"
  - function: "setResourceId"
  -  post:
      url: "/resource/{{ resourceId }}/subresource"
      json:
        body: "Example"

custom-code.js file containing the below function

function setResourceId(context, next) {
    const randomIndex = Math.round(Math.random() * context.vars.resources.length);
    context.vars.resourceId = context.vars.resources[randomIndex].id;
}