title: How to use .env vars in template string
body: <p>Using <code>.env</code> vars is straightforward as a key-value pair if you have setting defined as below in a <code>js</code> file.</p>
  
  <pre><code>export default {
    host: process.env.EMAIL_HOST,
    port: process.env.EMAIL_PORT,
    auth: {
      user: process.env.EMAIL_USER,
      pass: process.env.EMAIL_PASSWORD
    }
  };
  </code></pre>
  
  <p>However, I am wondering how can I use a <code>.env</code> var in a template string.</p>
  
  <p>Example</p>
  
  <pre><code>context.mailer.sendMail({
    from: `${settings.app.name} &lt;${process.env.EMAIL_HOST}&gt;`,
    to: user.email,
    subject: 'Subject',
    html: 'Some html',
  });
  </code></pre>
  
  <p>Over here <code>settings.app.name</code> is defined in the config file</p>
  
  <pre><code>export default {
    name: 'AppName',
  };
  </code></pre>
  
  <p>However, I can not use <code>process.env.EMAIL_HOST</code> in the <code>from</code> field as shown above.</p>