docs: Add example

Signed-off-by: Bo-Yi Wu <[email protected]>

Author: appleboy

README.md

@@ -4,3 +4,90 @@
 [![codecov](https://codecov.io/gh/golang-queue/nats/branch/main/graph/badge.svg?token=FFZN8E2ZZB)](https://codecov.io/gh/golang-queue/nats)
 
 NATS as backend with [Queue package](https://github.com/golang-queue/queue) (Connective Technology for Adaptive Edge & Distributed Systems)
+
+## Testing
+
+```sh
+go test -v ./...
+```
+
+## Example
+
+```go
+package main
+
+import (
+  "context"
+  "encoding/json"
+  "fmt"
+  "log"
+  "time"
+
+  "github.com/golang-queue/nats"
+  "github.com/golang-queue/queue"
+)
+
+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 := nats.NewWorker(
+    nats.WithAddr("127.0.0.1:4222"),
+    nats.WithSubj("example"),
+    nats.WithQueue("foobar"),
+    nats.WithRunFunc(func(ctx context.Context, m queue.QueuedMessage) error {
+      var v *job
+      if err := json.Unmarshal(m.Bytes(), &v); err != nil {
+        return err
+      }
+      rets <- v.Message
+      return nil
+    }),
+  )
+
+  // define the queue
+  q, err := queue.NewQueue(
+    queue.WithWorkerCount(10),
+    queue.WithWorker(w),
+  )
+  if err != nil {
+    log.Fatal(err)
+  }
+
+  // start the five worker
+  q.Start()
+
+  // 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()
+}
+```