startinf from version 3.0

Next, require the module and instantiate a mailgun client by calling new Mailgun(formData) and then using mailgun.client setup the client with basic auth credentials (username: 'api', key: 'key-yourkeyhere').

NOTE: startinf from version 3.0 you need to pass FormData (we need this to keep library universal). For node.js you can use form-data library.