Pre-allocating slice, avoid resizing

preallocate_slice.go

package main

import (
	"fmt"
	"time"
)

func main() {
	// Allocate a slice with a small capacity
	start := time.Now()
	s := make([]int, 0, 10)
	for i := 0; i < 100000; i++ {
		s = append(s, i)
	}
	elapsed := time.Since(start)
	fmt.Printf("Allocating slice with small capacity: %v\n", elapsed) // 1.165208ms

	// Allocate a slice with a larger capacity
	start = time.Now()
	s = make([]int, 0, 100000)
	for i := 0; i < 100000; i++ {
		s = append(s, i)
	}
	elapsed = time.Since(start)
	fmt.Printf("Allocating slice with larger capacity: %v\n", elapsed) // 361.333µs
}