Env property undefined in deployed serverless function

Describe the bug

I am connecting to my database in a serverless function. This works locally, but not once deployed. My database connection string is stored in a .env file. When deployed this string is undefined. The env file is committed and in the repo.

Github repo example - https://github.com/AshConnolly/next-env-issue

Here is my example .env file:

API_KEY='default-api-key'
CLIENT_KEY='default-client-key'
NEXT_PUBLIC_APP_LOCALE='en-us'
TEST='test'

When outputted into a page:

  <li>API_KEY='default-api-key' : {process.env.API_KEY}</li>
  <li>CLIENT_KEY='default-client-key' : {process.env.CLIENT_KEY}</li>
  <li>NEXT_PUBLIC_APP_LOCALE='en-us' : {process.env.NEXT_PUBLIC_APP_LOCALE}</li>
  <li>TEST='test' : {process.env.TEST}</li>

It shows only the value NEXT_PUBLIC_APP_LOCALE - as expected √.

However in a serverless function, it does not read my env variables correctly. This is what my serverless function looks like:

export default async (req, res) => {
  res.setHeader('Content-Type', 'application/json')
  res.statusCode = 200
  res.json({
    API_KEY: process.env.API_KEY,
    CLIENT_KEY: process.env.CLIENT_KEY,
    NEXT_PUBLIC_APP_LOCALE: process.env.NEXT_PUBLIC_APP_LOCALE,
    TEST: process.env.TEST,
  })
}

Expected behavior

Locally this shows correctly when i visit http://localhost:4000/api/test, outputting:

{
"API_KEY": "default-api-key",
"CLIENT_KEY": "default-client-key",
"NEXT_PUBLIC_APP_LOCALE": "en-us",
"TEST": "test"
}

Actual behavior when deployed

However when deployed it does not. it only shows the NEXT_PUBLIC_APP_LOCALE -

{
"NEXT_PUBLIC_APP_LOCALE": "en-us"
}

To Reproduce

Github repo - https://github.com/AshConnolly/next-env-issue Run locally, and deploy it to vercel to see the issue.

System information

Not applicable as its the deployment issue.

Why is this happening? Thanks! 👍

[timneutkens]

It was released on stable last night 👍

[AshConnolly]

You heroes! Thanks @ijjk @timneutkens! 😄