RoutePatternException: There is an incomplete parameter in the route template. Check that each '{' character has a matching '}' character. code example

Example: Microsoft.AspNetCore.Routing.Patterns.RoutePatternException: There is an incomplete parameter in the route template. Check that each '{' character has a matching '}' character.

app.UseMvc(routes => {
    routes.MapRoute(
        name: "custom",
        template: "{area:my area name}/{controller=AdminHome}/{action=Index}/{id?}");

    routes.MapRoute(
        name: "default",
        template: "{controller=Home}/{action=Index}/{id?}");
});