AWK Function syntax

Hi, I would like to know what is the correct syntax to perform a function in awk. Although I have seen several examples, not get it to work, this is what I'm trying:

#!/bin/bash

awk

function multi (number) {
  return number * 3
}
print multi (4)

Thanks

Hi,

awk '
function multi(number) {
  return number * 3
}
BEGIN{print multi(4);}'

Thanks!