According to Thich Nhat Hanh's wonderfully written biography of Gautama, "Old Path, White Clouds", buddha was served wrongly cooked mushrooms amongst other things, but in his compassion he went ahead and ate them anyway so as to not make the host feel bad. One might assume that he was quite old by then and ready to move on from this world..

Edit: Well my memory was pretty close, here's the actual passage:

https://imgur.com/a/06Zahtx

https://imgur.com/SB6mTTl