Go append slice speed comparison

main.go

package main

import (
	"fmt"
	"strconv"
	"sync"
	"time"
)

func method(f func()) func() {
	return func() {
		defer func(begin time.Time) {
			fmt.Println(time.Since(begin))
		}(time.Now())

		f()
	}
}

func routine(n int, f func()) func() {
	return func() {
		wg := &sync.WaitGroup{}
		wg.Add(n)
		for i := 0; i < n; i++ {
			go func() {
				defer wg.Done()
				f()
			}()
		}
		wg.Wait()
	}
}

func main() {
	n := 1000000
	numRoutine := 100

	method1 := func() {
		nums := []string{}
		for i := 0; i < n; i++ {
			nums = append(nums, strconv.Itoa(i))
		}
	}

	method2 := func() {
		nums := make([]string, n)
		for i := 0; i < n; i++ {
			nums[i] = strconv.Itoa(i)
		}
	}

	method3 := func() {
		nums := make([]string, 0, n)
		for i := 0; i < n; i++ {
			nums = append(nums, strconv.Itoa(i))
		}
	}

	method(routine(numRoutine, method1))()
	method(routine(numRoutine, method2))()
	method(routine(numRoutine, method3))()
}