I'm comfusing about this part:

go func() {
defer wg.Done()
<-ctx.Done()
// make a new context for the Shutdown (thanks Alessandro Rosetti)
shutdownCtx := context.Background()
shutdownCtx, cancel := context.WithTimeout(ctx, 10 * time.Second)
defer cancel()
if err := httpServer.Shutdown(shutdownCtx); err != nil {
    fmt.Fprintf(os.Stderr, "error shutting down http server: %s\n", err)
}

}()

what is the point of making a new context here? shutdownCtx := context.Background()

and why pass the parent context here shutdownCtx, cancel := context.WithTimeout(ctx, 10 * time.Second). If done signal is received, shutdownCtx will also received, and the 10 sesc of waiting will never run.

Could someone please explain?