There isn't much relation between the two, or to use a more technical term, correlation. Gold is a precious metal that has been used for thousands of years, while Bitcoin is a cryptocurrency. Gold's price movement is more stable while the price of Bitcoin has been especially volatile lately. And, analysis done between them shows that the correlation is close to zero.
 
There is something similar about them though; Both Gold and Bitcoin are thought of as safe assets by investors. So probably in certain financial situations, when investors are trying to get out of the cash position that they might be holding and are looking for a safe place to put their money, and this maybe because of national monetary policies or the state the global economy is in, both Bitcoin and Gold are two of the best candidates.