fib.go

package main

import (
  "os"
  "strconv"
)

func fibonacci(n int) uint64 {
  if n > 0 {
    return fibonacci(n - 1) * uint64(n);
  }

  return uint64(1);
}

func main() {
  in, _ := strconv.Atoi(os.Args[1])
  println(fibonacci(in))
}