To make the sauce, put the beer, garlic and lemon zest in a small pan over high heat. Reduce by half then add the lemon juice, Worcestershire, corn syrup, and crab boil. Reduce to ¼ cup.Remove from heat and whisk in the cold butter, one tablespoon at a time.Meanwhile heat a grill over high heat.Thread the shrimp and sausage onto metal skewers, alternating as you go. Sprinkle with salt and black pepper.When grill is hot, baste some of the sauce onto the skewers and grill for 1 to 3 minutes per side, until shrimp are cooked through. Baste with more of the sauce as you go.Serve immediately with lemon wedges, if desired.