How to set up subdomain on ngrok and run on node?

Question

Node.js

Good afternoon!
How to set up subdomain on ngrok and run on node?
Maybe I didn’t understand (didn’t see it in the docks ) and is this part of a paid subscription?
The code:

app.listen(config.get('port'), function() {
  return console.log('Listening on port', config.get('port'));
});

ngrok.connect({
  authtoken: 'mytoken ***',
  subdomain: 'mysub',
  port: config.get('port')
}, function(err, url) {
  return console.log('url: ', url, '\nerr: ', err);
});

Thank you!

Answer 1

Paid. :(
I found this line in the docks:
Reserved domains will never be assigned to another user, even if your tunnel is offline. Custom hostnames via CNAME must be reserved for security reasons.
And this button will appear only when you make a paid subscription.