Joining the military for the sole reason of using your training to eventually become a civilian cargo pilot is probably not going to work out very well.

Last I knew, the commitment required after receiving your wings in the USAF (about a year of training) is 10 years. If you spend 10 years of your life with an eye on the door, wondering when it will end, you're not going to be very effective in your mission.

I'm not saying you can't have a general career plan mapped out and even be very certain you won't spend a full 20 year career in the military. However, while you are in, the level of effort, commitment and personal sacrifice is not something you will be able to provide consistently if you're only there to get ratings.