/**
   * Marks this step as the last step in the {@code ClosingFuture} pipeline. When this step is done,
   * {@code receiver} will be called with an object that contains the result of the operation. The
   * receiver can store the {@link ValueAndCloser} outside the receiver for later synchronous use.
   *
   * <p>After calling this method, you may not call {@link #finishToFuture()}, this method again, or