title: Swagger Hub `Try it out` returns TypeError: Failed to fetch for localhost when using browser option
body: <p>I am trying to test my API documentation using <code>openapi: 3.0.1</code> format. When trying to execute the endpoints from Swagger Hub documentation, I get <code>TypeError: Failed to fetch</code>. </p>
  
  <p>The curl command that is shown runs fine from terminal: </p>
  
  <pre><code>curl -X GET "http://localhost:3030/services" -H "accept: application/json; charset=UTF-8"
  </code></pre>
  
  <p>The issue is both for Safari as well as Chrome browsers.</p>
  
  <p>I have also enabled CORS for my golang application as per the following snippet:</p>
  
  <pre><code>allowedOrigins := handlers.AllowedOrigins([]string{"*"})
  allowedCredentials := handlers.AllowCredentials()
  exposedHeaders := handlers.ExposedHeaders([]string{"Content-Length", "ETag", "Link", "X-RateLimit-Limit", "X-RateLimit-Remaining"})
  
  log.Fatal(http.ListenAndServe(":3030", handlers.CORS(allowedOrigins, allowedCredentials, exposedHeaders)(router)))
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/PlQbl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PlQbl.png" alt="enter image description here"></a></p>