check for context cancelled errors using errors.Is (#39)

Co-authored-by: mlctrez <mlctrez@gmail.com>
Reviewed-on: https://git.mills.io/prologic/msgbus/pulls/39
Reviewed-by: James Mills <james@mills.io>
Co-authored-by: mlctrez <mlctrez@noreply@mills.io>
Co-committed-by: mlctrez <mlctrez@noreply@mills.io>

client/client.go

@@ -235,7 +235,7 @@ func (s *Subscriber) connect(ctx context.Context) (*websocket.Conn, error) {
 		conn, _, err := websocket.Dial(ctx, url, nil)
 		if err != nil {
 			log.WithError(err).Debugf("dial error")
-			if err == context.Canceled {
+			if errors.Is(err, context.Canceled) {
 				return nil, err
 			}
 			log.Debugf("reconnecting in %s", b.Duration())

client/client_test.go

@@ -1,10 +1,12 @@
 package client
 
 import (
+	"context"
 	"io/ioutil"
 	"net/http/httptest"
 	"os"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -39,3 +41,50 @@ func TestClientPublish(t *testing.T) {
 	assert.Equal(topic, msg.Topic)
 	assert.Equal([]byte("hello world"), msg.Payload)
 }
+
+func TestCancelContextOnSubscribe(t *testing.T) {
+
+	assert := assert.New(t)
+	require := require.New(t)
+
+	logDir, err := ioutil.TempDir("", "msgbus-logs-*")
+	require.NoError(err)
+	defer os.RemoveAll(logDir)
+
+	mb, err := msgbus.NewMessageBus(msgbus.WithLogPath(logDir))
+	require.NoError(err)
+	defer os.RemoveAll(logDir)
+
+	server := httptest.NewServer(mb)
+	defer server.Close()
+
+	client := NewClient(server.URL, nil)
+
+	sub := client.Subscribe("hello", 1, func(msg *msgbus.Message) error { return nil })
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	failAfter := time.NewTimer(5 * time.Second)
+
+	errChan := make(chan error)
+	go func() {
+		errChan <- sub.Run(ctx)
+	}()
+
+	loop := true
+	for loop {
+		select {
+		case <-failAfter.C:
+			loop = false
+			t.Fatal("Run() with cancelled context did not exit on time")
+		case runError := <-errChan:
+			loop = false
+			assert.ErrorIs(runError, context.Canceled)
+		}
+	}
+
+	cancel()
+	<-ctx.Done()
+
+}