title: environment variables with capistrano 3
body: <p>What is the best way to add environment variables with capistrano 3?</p>
  
  <p>I've tried both</p>
  
  <pre><code>set :default_env, { 
    'MAILCHIMP' =&gt; 'verylongstring'
  }
  </code></pre>
  
  <p>and</p>
  
  <pre><code>set :default_environment, { 
    'MAILCHIMP' =&gt; 'verylongstring',
  }
  </code></pre>
  
  <p>but none seemed to do anything usefull.</p>