code: func (c *Client) DumpPrivKey(address btcutil.Address) (*btcutil.WIF, error) {
  	return c.DumpPrivKeyAsync(address).Receive()
  }
docs: // DumpPrivKey gets the private key corresponding to the passed address encoded
  // in the wallet import format (WIF).
  //
  // NOTE: This function requires to the wallet to be unlocked.  See the
  // WalletPassphrase function for more details.