database/sql: fix nits in test

Change-Id: I451b33d8da8d97917f2b257e6a25392c6e6582db
Reviewed-on: https://go-review.googlesource.com/36671
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/database/sql/sql_test.go

@@ -316,7 +316,7 @@ func TestQueryContext(t *testing.T) {
 	select {
 	case <-ctx.Done():
 		if err := ctx.Err(); err != context.Canceled {
-			t.Fatalf("context err = %v; want context.Canceled")
+			t.Fatalf("context err = %v; want context.Canceled", err)
 		}
 	default:
 		t.Fatalf("context err = nil; want context.Canceled")
@@ -365,7 +365,8 @@ func TestQueryContextWait(t *testing.T) {
 	defer closeDB(t, db)
 	prepares0 := numPrepares(t, db)
 
-	ctx, _ := context.WithTimeout(context.Background(), time.Millisecond*15)
+	ctx, cancel := context.WithTimeout(context.Background(), time.Millisecond*15)
+	defer cancel()
 
 	// This will trigger the *fakeConn.Prepare method which will take time
 	// performing the query. The ctxDriverPrepare func will check the context
@@ -386,7 +387,8 @@ func TestTxContextWait(t *testing.T) {
 	db := newTestDB(t, "people")
 	defer closeDB(t, db)
 
-	ctx, _ := context.WithTimeout(context.Background(), time.Millisecond*15)
+	ctx, cancel := context.WithTimeout(context.Background(), time.Millisecond*15)
+	defer cancel()
 
 	tx, err := db.BeginTx(ctx, nil)
 	if err != nil {