Unless you have experience keeping Coluber and related snakes, your best bet is to release him where you found him. Wild- caught racers stress easily from capture and from captivity and are often very difficult to acclimate.
If you are intent on keeping him anyway, then you should concentrate on getting him feeding for you first. These are very active snakes and will require a large enclosure with plenty of hiding options and a place to bask. They will eat a lot of different things, but probably won't eat at all if they aren't comfortable with the surroundings. You will need to leave him alone entirely except for cleaning his cage. He will most likely refuse dead food at first. I would offer live crawler or hopper mice to begin with. Once he starts to feed on them and will take two at a meal, then offer one live one and one frozen/thawed. Once he starts to take the frozen/thawed one as well as the live one, then you can get him off live ones.
If you try to tame him before you get him feeding, he will starve to death. It will be a long time before he tames to any appreciable degree if he ever does. The most likely thing is that he will start gnawing on you the minute you pick him up and stop when you put him down.
Most of the snakes in the genus Coluber are that way. Probably the meanest snake I ever owned in my life, and that includes some pretty ferocious elapids, viperids and crotalids, was a 4 foot Coluber hippocrepis. That snake was pure evil and never tamed one little bit the whole time I had him. He was a voracious feeder, but was literally "mean as a snake". I've kept a few North American Coluber also, and have never really seen a "tame" one that I can recall.
One other problem with wild-caught Coluber is that they tend to carry a pretty good load of parasites. The stress from capture and captivity can cause an immune system depression which allows this load to become overwhelming and they will often die from this within a couple of months of capture. If the snake does not begin feeding within about a month of capture, I would definitely recommend releasing it where you found it.