title: How to use the API KEY in google shopping
body: <p>Im trying to execute a method of content API, so, when I test the follow URL:</p>
  
  <pre><code>https://www.googleapis.com/content/v2.1/accounts/authinfo?key={YOUR_API_KEY}
  </code></pre>
  
  <p>The call of the service retrieves me:</p>
  
  <pre><code>{
   "error": {
    "errors": [
     {
      "domain": "global",
      "reason": "required",
      "message": "Login Required",
      "locationType": "header",
      "location": "Authorization"
     }
    ],
    "code": 401,
    "message": "Login Required"
   }
  }
  </code></pre>
  
  <p>But still show me the same error. Please any guide of this integration, I need call it from a C# console application, not by web site app with OAuth2.</p>