Slow Cooker Shredded Pork

1 (15-ounce) can tomato sauce 3 tablespoons chili powder 3 tablespoons light brown sugar 2 teaspoons ground coriander 1 teaspoon ground cumin 1 (3-pound) pork shoulder (or butt), trimmed of excess fat Kosher salt and freshly cracked black pepper 5 cloves garlic, minced or grated 2 yellow onions, diced 1/4 cup fresh lime juice