Exercise: power by recursion

Write a recursive function func power(base, exp int) int that returns base raised to the power exp.

• power(2, 10) → 1024
• power(-2, 3) → -8
• power(7, 0) → 1

Constraints: exp is from 0 to 18, base is from -10 to 10 and may be negative or zero; any number to the power 0 is 1, including power(0, 0), and the result always fits in an int.

Do not add extra imports unless the task says so explicitly.