title: How to inject port and host using ENV variable in Create React App Proxy settings?
body: <p>Is it possible to set proxy settings in CRA differently than with package.json? For example using ENV variables?</p>
  
  <p>From CRA <a href="https://github.com/facebookincubator/create-react-app/blob/master/packages/react-scripts/template/README.md#proxying-api-requests-in-development" rel="noreferrer">docs</a> it states</p>
  
  <blockquote>
    <p>Use environment variables to inject the right server host and port into your app.</p>
  </blockquote>
  
  <p>Is this sentence about proxy or dev server itself?</p>
  
  <p>According to the <a href="https://github.com/facebookincubator/create-react-app/blob/2e82ebb3371731a5c4e346f310848ddb23fd0976/packages/react-dev-utils/WebpackDevServerUtils.js#L266" rel="noreferrer">this</a> and <a href="https://github.com/facebookincubator/create-react-app/blob/2e82ebb3371731a5c4e346f310848ddb23fd0976/packages/react-scripts/scripts/start.js#L69" rel="noreferrer">this</a>, the only way to influence proxy settings is via package.json.</p>