How to define the configuration property in node.js in windows?

Here z my two files under folder config:default.json

{"jwtPrivateKey": ""}

Here z my custom-environment-varaibles.json

{"jwtPrivateKey": "startup_jwtPrivateKey"}

And i am accessing the property from this file users.js

router.post('/signin', async (req, res) => {  const { error } = validateLogin(req.body);   if (error) return res.status(400).send(error.details[0].message);  let user = await User.findOne({ email: req.body.email });  if (!user) return res.status(400).send('No user found with the given credentials.');  const matchPassword = await bcrypt.compare(req.body.password, user.password)  if (!matchPassword) return res.status(400).send('Invalid password')  const token = jwt.sign({ _id: user._id}, config.get('jwtPrivateKey'))  res.send(token)})

I have tried to manually set the variable "startup_jwtPrivateKey" to some value (i.e. not using the command) .And then i tried to set the variable "startup_jwtPrivateKey" to some value using this command set startup_jwtPrivateKey=mySecret . But still i am getting this error

throw new Error('Configuration property "'+ property +'" is not defined');    ^Error: Configuration property "jwtPrivatekey" is not defined

Here z my app.js file

if (!config.get('jwtPrivatekey')) {  console.error('Fatal error: config settings is not defined.')  process.exit(1);}