Add ServeAsync Handler to process message in new goroutine (#87)

serveasync.go

@@ -0,0 +1,27 @@
+// Copyright 2020 The mqtt-go authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mqtt
+
+// ServeAsync is a MQTT message handler to process messages asynchronously.
+type ServeAsync struct {
+	// Handler is an underlying handler.
+	// Handler.Serve() will be called asynchronously.
+	Handler
+}
+
+// Serve the message in a new goroutine.
+func (m *ServeAsync) Serve(message *Message) {
+	go m.Handler.Serve(message.clone())
+}

serveasync_test.go

@@ -0,0 +1,50 @@
+// Copyright 2020 The mqtt-go authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mqtt
+
+import (
+	"bytes"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestServeAsync(t *testing.T) {
+	processed := make(chan byte, 10)
+	var wg sync.WaitGroup
+
+	s := &ServeAsync{HandlerFunc(func(m *Message) {
+		time.Sleep(time.Duration(m.Payload[1]) * time.Millisecond)
+		processed <- m.Payload[0]
+		wg.Done()
+	})}
+
+	wg.Add(3)
+	s.Serve(&Message{Payload: []byte{0x00, 0x10}})
+	s.Serve(&Message{Payload: []byte{0x01, 0x08}})
+	s.Serve(&Message{Payload: []byte{0x02, 0x18}})
+	wg.Wait()
+	close(processed)
+
+	var order []byte
+	for id := range processed {
+		order = append(order, id)
+	}
+
+	expected := []byte{0x01, 0x00, 0x02}
+	if !bytes.Equal(expected, order) {
+		t.Errorf("Order of the process is expected to be: %v, got: %v", expected, order)
+	}
+}