code: func (c *Client) InvalidateBlockAsync(blockHash *chainhash.Hash) FutureInvalidateBlockResult {
  	hash := ""
  	if blockHash != nil {
  		hash = blockHash.String()
  	}
  
  	cmd := btcjson.NewInvalidateBlockCmd(hash)
  	return c.sendCmd(cmd)
  }
docs: // InvalidateBlockAsync returns an instance of a type that can be used to get the
  // result of the RPC at some future time by invoking the Receive function on the
  // returned instance.
  //
  // See InvalidateBlock for the blocking version and more details.