What is the current behavior?

The _substituteVars function throws an illegal key type for substitution map if it encounters and array while mapping the variables in the custom-environment-variables.json
*Create custom-environment-variables.json file and add a properties to pull values from env file:

"services": {
"messagehub": [
{
"label": "messagehub",
"credentials": {
"api_key": "API_KEY", // from env
"kafka_rest_url": "REST_URL" // from env
}
}
]
}
`

What is the expected behavior?

The _substituteVars function in config.js throws an error. Illegal key type for substitution map at components.services: object as the function is only validating 'strings' and 'objects' and since I've an

Please tell us about your environment:

• node-config version: 1.29.4
• node-version: 9.0