code: func (r FutureGetBlockCountResult) Receive() (int64, error) {
  	res, err := receiveFuture(r)
  	if err != nil {
  		return 0, err
  	}
  
  	// Unmarshal the result as an int64.
  	var count int64
  	err = json.Unmarshal(res, &count)
  	if err != nil {
  		return 0, err
  	}
  	return count, nil
  }
docs: // Receive waits for the response promised by the future and returns the number
  // of blocks in the longest block chain.