Add PubSub.ChannelSize

pubsub.go

@@ -400,14 +400,30 @@ func (c *PubSub) ReceiveMessage() (*Message, error) {
 //
 // If the Go channel is full for 30 seconds the message is dropped.
 func (c *PubSub) Channel() <-chan *Message {
-	c.chOnce.Do(c.initChannel)
+	return c.channel(100)
+}
+
+// ChannelSize is like Channel, but creates a Go channel
+// with specified buffer size.
+func (c *PubSub) ChannelSize(size int) <-chan *Message {
+	return c.channel(size)
+}
+
+func (c *PubSub) channel(size int) <-chan *Message {
+	c.chOnce.Do(func() {
+		c.initChannel(size)
+	})
+	if cap(c.ch) != size {
+		err := fmt.Errorf("redis: PubSub.Channel is called with different buffer size")
+		panic(err)
+	}
 	return c.ch
 }
 
-func (c *PubSub) initChannel() {
+func (c *PubSub) initChannel(size int) {
 	const timeout = 30 * time.Second
 
-	c.ch = make(chan *Message, 100)
+	c.ch = make(chan *Message, size)
 	c.ping = make(chan struct{}, 1)
 
 	go func() {