code: func dsContext(c context.Context) context.Context {
  	c = info.MustNamespace(c, DatastoreNamespace)
  	return dscache.AddShardFunctions(c, func(*datastore.Key) (shards int, ok bool) {
  		return 0, true
  	})
  }
docs: // dsContext is used for all datastore accesses that touch 'instance' entities.
  //
  // It switches the namespace and disables dscache, since these entities are
  // updated from Flex, which doesn't work with dscache. Besides, all reads happen
  // either in transactions or through queries - dscache is useless anyhow.