I am going on 40 next month是什么意思？

这里的on是什么意思？

i am on it I find out what is going on while I am there,pretending to control my two -year-old son. I think I am going to quit my job soon. It is probably time for me to move on. i am going to shanghai tommorrow。 i am going to be an interpreter I am going riding this afternoon i am going to get you good. 请教i am going to play i am going to do my home work.~~am going to do ~是谓语？ I am really gone on you是什么意思?