Why I can't match the .html suffix in router?

I want to match the .html suffix.

For example, the default index page is 

https://localhost:44354/home/index

I want to match this URL also

https://localhost:44354/home/index.html

I added these codes in startup.cs

app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}.html/{id?}");
});

After the program ran, it reports this error:

An unhandled exception occurred while processing the request.
AmbiguousMatchException: The request matched multiple endpoints. Matches:

WebApplication1.Controllers.HomeController.Index (WebApplication1)
WebApplication1.Controllers.HomeController.Privacy (WebApplication1)
WebApplication1.Controllers.HomeController.Error (WebApplication1)
Microsoft.AspNetCore.Routing.Matching.DefaultEndpointSelector.ReportAmbiguity(CandidateState[] candidateState)

Stack Query Cookies Headers Routing
AmbiguousMatchException: The request matched multiple endpoints. Matches: WebApplication1.Controllers.HomeController.Index (WebApplication1) WebApplication1.Controllers.HomeController.Privacy (WebApplication1) WebApplication1.Controllers.HomeController.Error (WebApplication1)
Microsoft.AspNetCore.Routing.Matching.DefaultEndpointSelector.ReportAmbiguity(CandidateState[] candidateState)
Microsoft.AspNetCore.Routing.Matching.DefaultEndpointSelector.ProcessFinalCandidates(HttpContext httpContext, CandidateState[] candidateState)
Microsoft.AspNetCore.Routing.Matching.DefaultEndpointSelector.Select(HttpContext httpContext, CandidateState[] candidateState)
Microsoft.AspNetCore.Routing.Matching.DfaMatcher.MatchAsync(HttpContext httpContext)
Microsoft.AspNetCore.Routing.Matching.DataSourceDependentMatcher.MatchAsync(HttpContext httpContext)
Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.Invoke(HttpContext httpContext)
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.TryServeStaticFile(HttpContext context, string contentType, PathString subPath)
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.HttpsPolicy.HttpsRedirectionMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Show raw exception details

Why it matched multiple endpoints? How can I solve it? Thank you.