My version of this code

recursion.go

// Recursion vs loops example in Go
package main

import (
	"fmt"
	"time"
)

const until = 42

func recursion(n int) {
	fmt.Print(".")
	n++
	if n <= until {
		recursion(n)
	} else {
		fmt.Println("done")
	}
}

func loop(n int) {
	for n <= until {
		fmt.Print(".")
		n++
	}
	fmt.Println("done")
}

func timeMethod(m string, f func(n int)) {
	fmt.Printf("%s method:\n", m)
	start := time.Now()
	f(0)
	duration := time.Since(start)
	fmt.Println("Took", duration)
}

func main() {
	timeMethod("Loop", loop)
	timeMethod("Recursion", recursion)
}