internal/processtest: fix the timeout logic

Updates #2571

internal/processtest/testdata/issue2079.go

@@ -43,17 +43,17 @@ func (g *Game) Layout(width, height int) (int, int) {
 	done := make(chan struct{})
 	timeout := time.After(time.Second)
 	go func() {
+		i := ebiten.NewImage(width, height)
+		i.Fill(color.White)
+		i.Dispose()
+		close(done)
+	}()
+
 	select {
 	case <-done:
 	case <-timeout:
 		panic("timeout")
 	}
-	}()
-	defer close(done)
-
-	i := ebiten.NewImage(width, height)
-	i.Fill(color.White)
-	i.Dispose()
 	return width, height
 }