feat(options): panic when options are nil (#3363)

Client creation should panic when options are nil.

osscluster.go

@@ -924,6 +924,9 @@ type ClusterClient struct {
 // NewClusterClient returns a Redis Cluster client as described in
 // http://redis.io/topics/cluster-spec.
 func NewClusterClient(opt *ClusterOptions) *ClusterClient {
+	if opt == nil {
+		panic("redis: NewClusterClient nil options")
+	}
 	opt.init()
 
 	c := &ClusterClient{