Adding gtk3 accelerators in C

I'm trying to implement accelerators in gtk3 for my app. I found out how to do it from a post on github.

#include <stdio.h>
#include <gtk/gtk.h>

// This is a callback that will be called when the accelerator is
// pressed.
void accelerator_pressed(void)
{
    printf("accelerator_pressed\n");
}

int main(int argc, char** argv)
{
    gtk_init(&argc, &argv);

    GtkWidget* window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    GClosure* closure = g_cclosure_new(accelerator_pressed, 0, 0);

    // Set up the accelerator group.
    GtkAccelGroup* accel_group = gtk_accel_group_new();
    gtk_accel_group_connect(accel_group,
                            GDK_KEY_A,
                            GDK_CONTROL_MASK,
                            0,
                            closure);
    gtk_window_add_accel_group(GTK_WINDOW(window), accel_group);

    // Quit the app when the window is closed.
    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

    // Display the top level window.
    gtk_widget_show(window);

    gtk_main();

    return 0;
}

My question is how to implement it without creating a window.