docs: update example

Author: appleboy

_example/single/go.mod

@@ -2,7 +2,7 @@ module example
 
 go 1.18
 
-require github.com/golang-queue/queue v0.0.13-0.20220403053548-d431277d570f
+require github.com/golang-queue/queue v0.0.13-0.20220408035349-ed24fa14aa00
 
 require (
 	github.com/golang-queue/nsq v0.0.0-00010101000000-000000000000

_example/single/go.sum

@@ -1,6 +1,7 @@
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
-github.com/golang-queue/queue v0.0.13-0.20220403053548-d431277d570f h1:Wioq3g97ssizNPQsPwdL61DIjePabPaq+XYo7z2t2Oc=
-github.com/golang-queue/queue v0.0.13-0.20220403053548-d431277d570f/go.mod h1:KD9age1s6nk8Evz3tfKHsk8k4LwA0htxQ7MS7rJPJzA=
+github.com/golang-queue/queue v0.0.13-0.20220408035349-ed24fa14aa00 h1:EFiINOvAuGgxiE3MNu7PKY0O2Pvvc7r6YApdqAnhWnQ=
+github.com/golang-queue/queue v0.0.13-0.20220408035349-ed24fa14aa00/go.mod h1:g1yxxDl8JMo4gUfxt11fjjU3SXU1ah61EvwshmDoSIs=
+github.com/golang/mock v1.6.0 h1:ErTB+efbowRARo13NNdxyJji2egdxLGQhRaY+DUumQc=
 github.com/golang/snappy v0.0.1 h1:Qgr9rKW7uDUkrbSmQeiDsGa8SjGyCOGtuasMWwvp2P4=
 github.com/golang/snappy v0.0.1/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/nsqio/go-nsq v1.1.0 h1:PQg+xxiUjA7V+TLdXw7nVrJ5Jbl3sN86EhGCQj4+FYE=

_example/single/main.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/golang-queue/nsq"
 	"github.com/golang-queue/queue"
+	"github.com/golang-queue/queue/core"
 )
 
 type job struct {
@@ -34,7 +35,7 @@ func main() {
 		nsq.WithChannel("foobar"),
 		// concurrent job number
 		nsq.WithMaxInFlight(10),
-		nsq.WithRunFunc(func(ctx context.Context, m queue.QueuedMessage) error {
+		nsq.WithRunFunc(func(ctx context.Context, m core.QueuedMessage) error {
 			var v *job
 			if err := json.Unmarshal(m.Bytes(), &v); err != nil {
 				return err