title: StackExchange.Redis HGET/HGETASYNC returns null when hash key is GUID
body: <p>I'm experiencing some issue and I believe it might be a bug in <em>StackExchange.Redis</em> library.</p>
  
  <p>When I create a hash where keys are GUID, both <code>.HashGet</code> or <code>HashGetAsync</code> will return a <code>null</code> value, while when I try to get the same hash key using <code>redis-cli</code> I'm able to retrieve the hash value successfully.</p>