Will being bound by an oath of silence hold up in court/questioning?

Basically I hang out with a fair few undesirables, and they tell me about all the illegal things they do, but only if I swear not to tell anyone, recently I've lost contact, and shouldn't be involved in any of their crimes from hence forth. I was just wondering, if I were questioned, surely an oath of silence would give me the right to remain silent. If not how can someone be expectedto take the oath in court seriously?