Slow Cooker Chicken Taco Soup

INGREDIENTS

• 1 onion, chopped
• 1 (16 ounce) can chili beans
• 1 (15 ounce) can black beans
• 1 (15 ounce) can whole kernel corn, drained
• 1 (8 ounce) can tomato sauce
• 1 (12 fluid ounce) can or bottle beer
• 2 (10 ounce) cans diced tomatoes with green chilies, undrained
• 1 (1.25 ounce) package taco seasoning
• 3 whole skinless, boneless chicken breasts
• shredded Cheddar cheese (optional)
• sour cream (optional)
• crushed tortilla chips (optional)