README Fix: Added client variable initialisation (redis.NewClient) in quickstartExampleClient() (#1257)

* updated: readme quickstart

Author: tansawit

README.md

@@ -56,6 +56,11 @@ func ExampleNewClient() {
 }
 
 func ExampleClient() {
+	client := redis.NewClient(&redis.Options{
+		Addr:     "localhost:6379",
+		Password: "", // no password set
+		DB:       0,  // use default DB
+	})
 	err := client.Set("key", "value", 0).Err()
 	if err != nil {
 		panic(err)