My father passed away and I've been working for the same company for almost 10 years, should I have expected my boss to attend the funeral or at least the mass?
Bosses and co-workers taking the time to address life changing events is always nice and appreciated, but whether you should expect that is entirely dependent on a multitude of factors that will vary wildly from company to company, role to role, job to job, and culture to culture.
I'd also never expect these by default. Work is work, personal life is personal life, and in many cultures, there is a purposeful separation between the two.
So for a boss to attend a wedding or funeral or Bar Mitzvah would typically be the exception rather than the norm, and only an exception when the above factors align (long time friend, small company, etc.)
My condolences on your loss.
I would have expected the boss to acknowledge the loss in some way. That could be attending a viewing or the funeral or sending flowers or a card or even an email. It could even be verbally extending his condolences to you. Depending on his schedule and the time/location of the funeral, it might not be possible to actually attend.
Unfortunately, if your boss has never had a severe loss of his own, he may not have realized how important it is you that he be there. If he didn't know the person, he may not have thought it appropriate to go. He also may be of a different religion than you are (or an atheist) and felt uncomfortable in going to a service from a different tradition.
There are also people who are uncomfortable with the idea of attending a funeral at all. Or he may even have had a loss of his own that going to the funeral would bring back up. I had a co-worker once who lost a child to cancer and he just couldn't go to other funerals. Everyone has their own emotional needs to tend to.
But we do not go to funerals for the dead but to support the living in their time of need. I know I didn't realize this until I lost my life partner. Since then I have made it a point to attend any local funerals or go to the funeral home for any coworker (not just subordinates) who has lost a family member.
If your boss's life experience hasn't led him to a similar conclusion, then at least release your own feeling of hurt rather than let it fester. If you have worked for him for ten years, you should have the measure of what kind of person he is and since you stayed that long, I assume he is mostly a decent person. I would not be surprised if he is unaware that he hurt you. Instead of dwelling on it, remember how much it hurt you (my assumption just because you felt the need to ask this question) and do as I did and go to other employee's funerals when they come up. That is a more postive way of dealing with the hurt by seeing to it that you do not hurt someone else the same way.
My condolences on your loss, it is very difficult to go through these things.