title: shopify-api-node returns status 401 unauthorized for private app
body: <p>I am attempting to make a NodeJS application utilizing this npm package called <a href="https://www.npmjs.com/package/shopify-api-node" rel="nofollow noreferrer">shopify-node-api</a></p>
  
  <p>Please note, this is a <strong>private</strong> app which was generated in the Shopify Partners account. I've passed the <code>shopName</code>, <code>apiKey</code> and <code>password</code> as instructed by the documentation. </p>
  
  <pre><code>    const Shopify = require('shopify-api-node');
  
      const shopify = new Shopify({
        shopName: 'your-shop-name',
        apiKey: 'your-api-key',
        password: 'your-app-password'
      });
  </code></pre>
  
  <p>However, when attempting to perform something as straightforward as this <strong>GET</strong>:</p>
  
  <pre><code>    shopify.product.get()
      .then(products =&gt;  res.send(products))
      .catch(err =&gt; res.send(err));
  </code></pre>
  
  <p>I receive:</p>
  
  <pre><code>    {
          "name": "HTTPError",
          "hostname": "your-shop-name",
          "method": "GET",
          "path": "/admin/products.json",
          "protocol": "https:",
          "statusCode": 401,
          "statusMessage": "Unauthorized",
          "headers": {...}
      }
  </code></pre>
  
  <p>To all the Shopify App/JavaScript specialists, please advise on what I am overlooking?</p>