feat: add RequestContext to PubSubConn (gomodule#603)

Add a wrapper that goes through the standard receiveInternal
processing to match the API of the existing PubSubConn Receive
methods.

Fixes: gomodule#592

redis/pubsub.go

@@ -15,6 +15,7 @@
 package redis
 
 import (
+	"context"
 	"errors"
 	"time"
 )
@@ -116,6 +117,13 @@ func (c PubSubConn) ReceiveWithTimeout(timeout time.Duration) interface{} {
 	return c.receiveInternal(ReceiveWithTimeout(c.Conn, timeout))
 }
 
+// ReceiveContext is like Receive, but it allows termination of the receive
+// via a Context.  If the call returns due to cancellation of the context
+// the PubSubConn will have been closed.
+func (c PubSubConn) ReceiveContext(ctx context.Context) interface{} {
+	return c.receiveInternal(ReceiveContext(c.Conn, ctx))
+}
+
 func (c PubSubConn) receiveInternal(replyArg interface{}, errArg error) interface{} {
 	reply, err := Values(replyArg, errArg)
 	if err != nil {

redis/pubsub_test.go

@@ -15,6 +15,8 @@
 package redis_test
 
 import (
+	"context"
+	"errors"
 	"reflect"
 	"testing"
 	"time"
@@ -74,3 +76,25 @@ func TestPushed(t *testing.T) {
 		t.Errorf("recv /w timeout got %v, want %v", got, want)
 	}
 }
+
+func TestPubSubReceiveContext(t *testing.T) {
+	sc, err := redis.DialDefaultServer()
+	if err != nil {
+		t.Fatalf("error connection to database, %v", err)
+	}
+	defer sc.Close()
+
+	c := redis.PubSubConn{Conn: sc}
+
+	require.NoError(t, c.Subscribe("c1"))
+	expectPushed(t, c, "Subscribe(c1)", redis.Subscription{Kind: "subscribe", Channel: "c1", Count: 1})
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	got := c.ReceiveContext(ctx)
+	if err := got.(error); !errors.Is(err, context.Canceled) {
+		t.Errorf("recv w/canceled expected Canceled got %s", err.Error())
+	} else if err == nil {
+		t.Errorf("recv w/canceled ctx got %T %v, expected error", got, got)
+	}
+}