feathers/docs/guides/cli/custom-environment-variables.md

Custom Environment Variables

While node-config used for application configuration recommends to pass environment based configuration as a JSON string in a single NODE_CONFIG environment variable, it is also possible to use other environment variables via the config/custom-environment-variables.json file which looks like this by default:

{
  "port": {
    "__name": "PORT",
    "__format": "number"
  },
  "host": "HOSTNAME"
}

This sets app.get('port') using the PORT environment variable (if it is available) parsing it as a number and app.get('host') from the HOSTNAME environment variable.

See the node-config custom envrionment variable documentation for more information.