A constant hum coming from the ES Go pickup is usually a sign that there is a not a solid ground connection at the amplifier or audio device the guitar is plugged in to. If touching the metal end of the cable or the jack itself makes the noise get quieter or go away completely, you definitely have a grounding problem with your sound system or electrical outlet.

It's important to remember that when you have proper ground, no ground loops, and no electromagnetic interference, there will be no ground noise. The guitar or pickup itself does not create ground noise; it is simply affected by these conditions. Grounding issues can be frustrating and tough to track down, but it's in your best interest to identify the problem, not only for a quiet environment but also for a safe environment.