Fix PubSub panic on concurrent Close.

pool.go

@@ -415,12 +415,12 @@ func (p *stickyConnPool) put() (err error) {
 func (p *stickyConnPool) Put(cn *conn) error {
 	defer p.mx.Unlock()
 	p.mx.Lock()
-	if p.cn != cn {
-		panic("p.cn != cn")
-	}
 	if p.closed {
 		return errClosed
 	}
+	if p.cn != cn {
+		panic("p.cn != cn")
+	}
 	return nil
 }
 
@@ -433,15 +433,15 @@ func (p *stickyConnPool) remove() (err error) {
 func (p *stickyConnPool) Remove(cn *conn) error {
 	defer p.mx.Unlock()
 	p.mx.Lock()
+	if p.closed {
+		return errClosed
+	}
 	if p.cn == nil {
 		panic("p.cn == nil")
 	}
 	if cn != nil && p.cn != cn {
 		panic("p.cn != cn")
 	}
-	if p.closed {
-		return errClosed
-	}
 	if cn == nil {
 		return p.remove()
 	} else {

pubsub_test.go

@@ -235,8 +235,11 @@ var _ = Describe("PubSub", func() {
 		Expect(err).NotTo(HaveOccurred())
 		defer pubsub.Close()
 
+		var wg sync.WaitGroup
+		wg.Add(1)
 		go func() {
 			defer GinkgoRecover()
+			defer wg.Done()
 
 			time.Sleep(readTimeout + 100*time.Millisecond)
 			n, err := client.Publish("mychannel", "hello").Result()
@@ -248,6 +251,8 @@ var _ = Describe("PubSub", func() {
 		Expect(err).NotTo(HaveOccurred())
 		Expect(msg.Channel).To(Equal("mychannel"))
 		Expect(msg.Payload).To(Equal("hello"))
+
+		wg.Wait()
 	})
 
 	It("should reconnect on ReceiveMessage error", func() {
@@ -281,4 +286,24 @@ var _ = Describe("PubSub", func() {
 		wg.Wait()
 	})
 
+	It("should not panic on Close", func() {
+		pubsub, err := client.Subscribe("mychannel")
+		Expect(err).NotTo(HaveOccurred())
+		defer pubsub.Close()
+
+		var wg sync.WaitGroup
+		wg.Add(1)
+		go func() {
+			defer GinkgoRecover()
+
+			wg.Done()
+			_, err := pubsub.ReceiveMessage()
+			Expect(err).To(MatchError("redis: client is closed"))
+		}()
+		wg.Wait()
+
+		err = pubsub.Close()
+		Expect(err).NotTo(HaveOccurred())
+	})
+
 })