[RN 62] Variables are undefined

I installed react-native-config version 1.2.0 and added a .env file to the root of my project. This .env file contains the following:

REACT_APP_LAST_FM_API_KEY=some_key_here
REACT_APP_LAST_FM_SHARED_KEY=some_shared_key_here

In my App.tsx I’ve the following:

import Config from 'react-native-config';

console.log(Config.REACT_APP_LAST_FM_API_KEY) // undefined;

When I do console.log(Config) I get the following:

{"APPLICATION_ID": "com.mobile", "BUILD_TYPE": "debug", "DEBUG": true, "FLAVOR": "", "VERSION_CODE": 1, "VERSION_NAME": "1.0", "getConstants": [Function anonymous]}

Am I missing something?

Please let me know if you need any more information and thanks in advance!