What is probably happening is that the bore isn't totally dry before you lube it. I learned years ago that, once the bore is cleaned with hot water and soap, then flushed with hot water, immediately run several patches soaked with isopropyl alcohol, 99% strength. This can be found in the paint section of the hardware store. Don't use rubbing alcohol, it has around 30% water in it, and the idea is to use the alcohol to get the water out. Follow this with dry patches, then lube the bore.
As has been said by others, about any good lube can be used. Some folks swear by petroleum products, others swear at them. I have good success with olive oil (also called sweet oil in years gone by), but I have also been known to use Break Free CLP as the armorers taught us with the Mattel Toy.
Whatever you do, get the bore totally dry with alcohol after cleaning. Even having run hot water through the barrel so it is uncomfortable to hold won't evaporate all of the moisture out, and it will immediately start to rust. Lubing it does not stop that, it only covers the moisture in the bore, so you will still get rusty patches days or weeks later.
-WH-