StartupWithAuthenticationHandler.cs

public void ConfigureServices(IServiceCollectionservices)
{
    services.AddMemoryCache();
    services.AddHttpClient<IUserApiAuthenticationService, UserApiAuthenticationService>()
            .ConfigureHttpClient(c => c.BaseAddress ="http://urltotheuserapi.com");
    
    services.AddTransient<UserApiAuthenticationHandler>();
    services.AddHttpClient<UserService, UserService>()
            .ConfigureHttpClient(c => c.BaseAddress ="http://urltotheuserapi.com")
            .AddHttpMessageHandler<UserApiAuthenticationHanler>();
}