Load local file using Netlify functions

I've written a script which takes a JSON file and outputs it to an API endpoint using Netlify's Functions feature (https://functions.netlify.com/). For the most part, this works without a hitch, however, one of my endpoints has a lot of text and for ease of editing, I've split the large text blocks into markdown files which I then loaded into the endpoint.

Locally, this works perfectly, but when deployed I get a console error saying Failed to load resource: the server responded with a status of 502 (). I presume this is because I used a node fs method and Netlify doesn't allow that, however, I can't find any information about this.

The code I've used is here:

const marked = require('marked')
const clone = require('lodash').cloneDeep
const fs = require('fs')
const resolve = require('path').resolve
const data = require('../data/json/segments.json')

// Clone the object
const mutatedData = clone(data)

// Mutate the cloned object
mutatedData.map(item => {
  if (item.content) {
    const file = fs.readFileSync(resolve(`./src/data/markdown/${item.content}`), 'utf-8')
    item.content = marked(file)
  }
})

exports.handler = function(event, context, callback) {
  callback(null, {
    statusCode: 200,
    body: JSON.stringify({data: mutatedData})
  });
}

I've also attempted to replace

  const file = fs.readFileSync(resolve(`./src/data/markdown/${item.content}`), 'utf-8')

with

  const file = require(`../data/markdown/${item.content}`)

but that complains about a loader and I'd like to avoid adding webpack configs if possible as I'm using create-react-app, besides, I doubt it will help as I'd still be accessing the file-system after build time.

Has anyone else come across this issue before?