ABP - AuthenticationFilter is not working in controller

Question

I would like to implement some custom authentication logic, so I wrote an authentication filter. But for some reason, the AuthenticateAsync just never being called, which makes this attribute no use at all.

I have tested the same code in a normal web api project which works fine. Any ideas why this happens? And how can I debug to find the root cause of this scenario? I got nothing in the CallStack neither.

Here is the controller function:

    [HttpPost]
    [CustomAuthentication]
    public async Task<JsonResult> TestFunc(UserAccount user)
    {
        //controller logic
        return Json("blah");
    }

Here is the authentication filter:

public class CustomAuthenticationAttribute : Attribute, IAuthenticationFilter
{    
    public CustomAuthenticationAttribute()
    {
        var tt = "does it get in?";
    }

    public Task AuthenticateAsync(HttpAuthenticationContext context, CancellationToken cancellationToken)
    {
        var req = context.Request; // never being called
        //xxx authentication logic
        return Task.FromResult(0);                                          
    }                                                                       
 }