code: func (c *Client) GetNetworkHashPS2(blocks int) (int64, error) {
  	return c.GetNetworkHashPS2Async(blocks).Receive()
  }
docs: // GetNetworkHashPS2 returns the estimated network hashes per second for the
  // specified previous number of blocks working backwards from the most recent
  // block height.  The blocks parameter can also be -1 in which case the number
  // of blocks since the last difficulty change will be used.
  //
  // See GetNetworkHashPS to use defaults and GetNetworkHashPS3 to override the
  // height at which to calculate the estimate.