HttpContext.Current is null in custom IHttpHandlerFactory

HttpContext.Current is null in custom IHttpHandlerFactory

public class HandlerFactory : IHttpHandlerFactory
{
public IHttpHandler GetHandler(HttpContext context, string
requestType, string url, string pathTranslated)
{
// lots of code
}
public void ReleaseHandler(IHttpHandler handler)
{
// HttpContext.Current is always null here.
}
}
How can I make HttpContext.Current available (or use alternative approach
to store per-request variables such that they can be retrieved in
ReleaseHandler)?