code: func resourceVSphereDatastoreClusterReadCustomAttributes(d *schema.ResourceData, meta interface{}, pod *object.StoragePod) error {
  	client := meta.(*VSphereClient).vimClient
  	// Read custom attributes
  	if customattribute.IsSupported(client) {
  		log.Printf("[DEBUG] %s: Reading custom attributes", resourceVSphereDatastoreClusterIDString(d))
  		props, err := storagepod.Properties(pod)
  		if err != nil {
  			return err
  		}
  		customattribute.ReadFromResource(client, props.Entity(), d)
  	} else {
  		log.Printf("[DEBUG] %s: Custom attributes unsupported on this connection, skipping", resourceVSphereDatastoreClusterIDString(d))
  	}
  
  	return nil
  }
docs: // resourceVSphereDatastoreClusterReadCustomAttributes reads the custom
  // attributes for vsphere_datastore_cluster.