Snapped Node Application can't find certificates

I have a node application that is unable to locate the certificates while running as a snap. Running the application outside of a snap, it has no problem locating the certificates (while changing the file path up one directory).

Do I need to modify how the node application script calls for the certificates? For example in the script to be snapped:

const options = {
    certificateFile: "cert.pem",
    privateKeyFile: "private_key.pem"
}

Here is the yaml:

name: client # you probably want to 'snapcraft register <name>'
version: '1.0.0' # just for humans, typically '1.2+git' or '1.3.2'
summary: Single-line elevator pitch for your amazing snap # 79 char long summary
description: |
  This is my-snap's description. You have a paragraph or two to tell the
  most important story about your snap. Keep it under 100 words though,
  we live in tweetspace and your description wants to look good in the snap
  store.

grade: stable # must be 'stable' to release into candidate/stable channels
confinement: devmode # use 'strict' once you have the right plugs and slots

apps:
  node-service:
    command: bin/client
    daemon: simple
    restart-condition: always
    plugs: [network-bind]

parts:
  webserver:
    source: ./dist/
    plugin: nodejs
    node-engine: '8.11.0'

  certificates:
    source: ./certificates
    prime:
       - cert.pem
       - private_key.pem

make your application read the $SNAP environment variable and have this used a search prefix for cert.pem and private_key.pem in your script …