func lookupTrafficModel(trafficModel string, r *maps.DirectionsRequest) { switch trafficModel { case "optimistic": r.TrafficModel = maps.TrafficModelOptimistic case "best_guess": r.TrafficModel = maps.TrafficModelBestGuess case "pessimistic": r.TrafficModel = maps.TrafficModelPessimistic case "": // ignore default: log.Fatalf("Unknown traffic mode %s", trafficModel) } }