What is the electrolytic bath used in gold-plating of copper articles?

The answer is $AuCl\_3 + NaCN$


Now I understand that for electroplating, we need gold to be deposited on the copper article, and the electrolyte must enable that deposition. But I don’t know what is the use of $NaCN$ in the process. 


Also, if copper is the cathode, then pure gold should be the anode. But the oxidation potential of gold is very low, then how does it get dissolved in the solution. 


Can I get an explanation on this process would work?


