public void Configuration(IAppBuilder app)
{
var config = new HttpConfiguration();
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
//there you can pass func for getting username from token
//for more fine grained controll you can override StatefulTokenProvider.GetIdentityAsync
app.UseStatefulAuthentication((token)=>Task.FromResult(token == "abcxyz123" ? "JohnSmith" : null));
app.UseWebApi(config);
}