docs: update example

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

README.md

@@ -15,6 +15,94 @@ redis-server
 
 ![screen](/images/screen.png)
 
+start the redis cluster, see the [config](./conf/redis.conf)
+
+```sh
+# server 01
+mkdir server01 && cd server 01 && redis-server redis.conf --port 6379
+# server 02
+mkdir server02 && cd server 02 && redis-server redis.conf --port 6380
+```
+
+## Example
+
+For single server
+
+```go
+package main
+
+import (
+  "context"
+  "encoding/json"
+  "fmt"
+  "log"
+  "time"
+
+  "github.com/golang-queue/queue"
+  "github.com/golang-queue/redisdb"
+)
+
+type job struct {
+  Message string
+}
+
+func (j *job) Bytes() []byte {
+  b, err := json.Marshal(j)
+  if err != nil {
+    panic(err)
+  }
+  return b
+}
+
+func main() {
+  taskN := 100
+  rets := make(chan string, taskN)
+
+  // define the worker
+  w := redisdb.NewWorker(
+    redisdb.WithAddr("127.0.0.1:6379"),
+    redisdb.WithChannel("foobar"),
+    redisdb.WithRunFunc(func(ctx context.Context, m queue.QueuedMessage) error {
+      v, ok := m.(*job)
+      if !ok {
+        if err := json.Unmarshal(m.Bytes(), &v); err != nil {
+          return err
+        }
+      }
+
+      rets <- v.Message
+      return nil
+    }),
+  )
+
+  // define the queue
+  q := queue.NewPool(
+    5,
+    queue.WithWorker(w),
+  )
+
+  // assign tasks in queue
+  for i := 0; i < taskN; i++ {
+    go func(i int) {
+      if err := q.Queue(&job{
+        Message: fmt.Sprintf("handle the job: %d", i+1),
+      }); err != nil {
+        log.Fatal(err)
+      }
+    }(i)
+  }
+
+  // wait until all tasks done
+  for i := 0; i < taskN; i++ {
+    fmt.Println("message:", <-rets)
+    time.Sleep(50 * time.Millisecond)
+  }
+
+  // shutdown the service and notify all the worker
+  q.Release()
+}
+```
+
 ## Testing
 
 ```sh