go_sort.go

package main

import (
	"fmt"
	"sort"
	"time"
)

type FileInfo struct {
	FileName  string
	CreatedAt time.Time
}

func s_print(s []FileInfo, title string) {
	fmt.Println(title)
	for i, v := range s {
		fmt.Printf("%d: %s, %s\n", i, v.FileName, v.CreatedAt.Format(time.RFC3339))
	}
}

func main() {
	s := []FileInfo{
		{"file_middle", time.Now().Add(12 * time.Hour)},
		{"file_first", time.Now()},
		{"file_last", time.Now().Add(24 * time.Hour)},
	}

	s_print(s, "Before")
	// Before
	// 0: file_middle, 2020-08-09T01:25:46Z
	// 1: file_first, 2020-08-08T13:25:46Z
	// 2: file_last, 2020-08-09T13:25:46Z

	// sort by newest to oldest
	sort.Slice(s, func(i, j int) bool {
		return s[i].CreatedAt.After(s[j].CreatedAt)
	})

	s_print(s, "Sort by newest to oldest")
	// Sort by newest to oldest
	// 0: file_last, 2020-08-09T13:25:46Z
	// 1: file_middle, 2020-08-09T01:25:46Z
	// 2: file_first, 2020-08-08T13:25:46Z

	// sort by oldest to newest
	sort.Slice(s, func(i, j int) bool {
		return s[i].CreatedAt.Before(s[j].CreatedAt)
	})

	s_print(s, "Sort by oldest to newest")
	// Sort by oldest to newest
	// 0: file_first, 2020-08-08T13:25:46Z
	// 1: file_middle, 2020-08-09T01:25:46Z
	// 2: file_last, 2020-08-09T13:25:46Z
}