title: Getting a datastore entity into an interface in Go
body: <p>I have a couple of datastore Kinds that have the same field Id.  Is it possible to create one generic function that can get me this value?  Something similar to this?</p>
  
  <pre><code>var i interface{}
  err = datastore.Get(c, key, &amp;i)
  v := reflect.ValueOf(i)
  id := v.FieldByName("Id").String()
  </code></pre>
  
  <p>The above code, as it is, gives me a "datastore: invalid entity type" error.</p>