There are a few ways you can achieve that effect but most of the ways I can think of are kind of ugly, but this one is probably the cleanest.

Concept

Every few seconds, the player will get an enchanted golden apple. They will not be given one if they already have one.

Commands

Place a repeating always active command block with the command:

clear @a appleenchanted -1 1

Then a chain always active:

give @a appleenchanted

Set the delay of the first command block to how many seconds the cooldown should be multiplied by 20 (i.e. 10 seconds = 200).