title: Interpolation in rails when making an API request
body: <p>I have the following code in a controller action:</p>
  
  <pre><code>RestClient.post("https://api:#{ENV['MAILGUN_API_KEY']}" \
                    "@api.mailgun.net/v3/lists/#{ENV['MAILGUN_ALIAS']}/members",
                      :subscribed =&gt; true,
                      :address =&gt; email_address)
  </code></pre>
  
  <p>I am using .env gem to handle the environment variables. I am getting a 401 unauthorized error, however if I paste in the api key and alias, the request goes through. I can do a puts on ENV['MAILGUN_API_KEY'] and see the value in the console so I am not sure what the issue is.</p>