Exercise: clamp

Write a function func clamp(x *int, lo, hi int) that keeps the value of the variable x points to within the range from lo to hi. A value below lo becomes lo, and a value above hi becomes hi; a value inside the range stays as it is.

• n := 15, then clamp(&n, 0, 10) → n is 10
• n := -4, then clamp(&n, 0, 10) → n is 0
• n := 7, then clamp(&n, 0, 10) → n is 7

Constraints: x is not nil; lo <= hi, and the bounds may be equal; values at the bounds of the range do not change.

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