go bonk

1. For something to fail, break, mess up, rot, spoil, or become otherwise altered in a negative way. Can be used to describe someone who has gone crazy -or "bonkers"-, or something/someone who has passed away.
OR
2. To have intercourse (sex). (Can be used as "go bonk yourself" as well, but if you say that, you'll probably get laughed at. A lot.)

ex 1: "We've got everything set up. Hopefully, the plan will work and not go bonk."
ex 2: person 1:"They make such a cute couple!!!"

person 2:"They should just go bonk already and get it over with."