Gold is often flashed onto the pins of connectors in low voltage, low energy circuits. It prevents tarnishing.
The gold used in connector pins has a thickness of about 50 microinches. The manufacturers of circuit boards used to use much thicker deposits, but when the cost of gold zoomed the manufacturers cut back. That’s why the once-common practice of using Pink Pearl erasers to polish connections is a long-terminated “best practice”. By the way, gold plating on PCI expansion board connector tongues is a sign of quality — cheaper boards don’t use gold.