title: How to avoid CORS errors ("Failed to fetch" or "Server not found or an error occurred") when making requests from Swagger Editor?
body: <p>I have the following OpenAPI definition:</p>
  
  <pre class="lang-yaml prettyprint-override"><code>swagger: "2.0"
  
  info:
    version: 1.0.0
    title: Simple API
    description: A simple API to learn how to write OpenAPI Specification
  
  schemes:
    - https
  host: now.httpbin.org
  paths:
    /:
      get:
        summary: Get date in rfc2822 format
        responses:
          200:
            schema:
              type: object
              items:
                properties:
                  now:
                    type: object
                      rfc2822:
                        type: string
  </code></pre>
  
  <p>I would like to retrieve <code>rfc2822</code> from the <a href="https://now.httpbin.org/" rel="noreferrer">response</a>:</p>
  
  <pre><code>{"now": {"epoch": 1531932335.0632613, "slang_date": "today", "slang_time": "now", "iso8601": "2018-07-18T16:45:35.063261Z", "rfc2822": "Wed, 18 Jul 2018 16:45:35 GMT", "rfc3339": "2018-07-18T16:45:35.06Z"}, "urls": ["/", "/docs", "/when/:human-timestamp", "/parse/:machine-timestamp"]}  
  </code></pre>
  
  <p>But when I make a request from Swagger Editor, I get an error:</p>
  
  <blockquote>
    <p>ERROR Server not found or an error occurred</p>
  </blockquote>
  
  <p>What am I doing wrong?</p>