title: how can I solve this error in ionic `You must specify a "protocol" for the proxy type`
body: <p>I ran <code>ionic</code> start series <code>sidetabs</code> in my <code>Windows</code> and got this error</p>
  
  <p><a href="https://i.stack.imgur.com/7aY7A.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7aY7A.png" alt="enter image description here"></a></p>
  
  <pre><code>TypeError: You must specify a "protocol" for the proxy type (http, https, socks, socks4, socks4a, socks5, socks5h, pac+data, pac+file, pac+ftp, pac+http, pac+https)
      at new ProxyAgent (C:\Users\sato\AppData\Roaming\npm\node_modules\@ionic\cli-plugin-proxy\node_modules\proxy-agent\index.js:97:11)
      at ProxyAgent (C:\Users\sato\AppData\Roaming\npm\node_modules\@ionic\cli-plugin-proxy\node_modules\proxy-agent\index.js:81:45)
      at Request.proxy (C:\Users\sato\AppData\Roaming\npm\node_modules\@ionic\cli-plugin-proxy\node_modules\superagent-proxy\index.js:71:15)
      at C:\Users\sato\AppData\Roaming\npm\node_modules\ionic\node_modules\@ionic\cli-utils\lib\http.js:31:17
      at Generator.next (&lt;anonymous&gt;)
      at fulfilled (C:\Users\sato\AppData\Roaming\npm\node_modules\ionic\node_modules\tslib\tslib.js:102:62)
      at &lt;anonymous&gt;
  </code></pre>
  
  <p>How do I solve this?</p>