Brake light issue

[Outlaw87]

So the other day I went to get the ispection done on my 87 Silverado and it ended up failing because the driver side taillight wouldn't come on. They inspected and replaced the bulb and still nothing. Anyway, I came home Irritated but figured I could get it fixed. Well it's been a week and I still haven't fixed it. I've checked all connections, grounds, bulbs, and everything is kosher. Everything works fine except for the driver brake light, but it does come on from time to time and I think I may of figured something out today. If I wiggle the turn signal lever I can get the brake light to work. Does the signal lever switch have any control over the brake lights or is it a problem somewhere else? Also, if this is the problem, how difficult is it to fix?

Thanks in advance fellas...