Simple app which copies files to S3 with content type and modtime

main.go

package main

import (
	"context"
	"fmt"
	"io/fs"
	"mime"
	"os"
	"path/filepath"
	"time"

	"github.com/alecthomas/kong"
	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/service/s3"
	"github.com/aws/aws-sdk-go/aws"
	"github.com/rs/zerolog"
	"github.com/rs/zerolog/log"
)

const (
	metaMtime = "Mtime" // the meta key to store mtime in - e.g. X-Amz-Meta-Mtime
)

var (
	cfg struct {
		Debug     bool
		Version   kong.VersionFlag
		InputPath string
		Bucket    string
		Prefix    string
	}

	version string
)

func main() {
	kong.Parse(
		&cfg,
		kong.Vars{"version": version}, // bind a var for version
	)

	log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr})
	zerolog.SetGlobalLevel(zerolog.InfoLevel)

	if cfg.Debug {
		zerolog.SetGlobalLevel(zerolog.DebugLevel)
	}

	ctx := context.Background()

	awscfg, err := config.LoadDefaultConfig(ctx)
	if err != nil {
		log.Fatal().Err(err).Msg("failed to configure sdk")
	}

	client := s3.NewFromConfig(awscfg)

	err = fs.WalkDir(os.DirFS(cfg.InputPath), ".", func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		fin, err := d.Info()
		if err != nil {
			return err
		}

		fmt.Printf("path=%q, isDir=%v mod=%v\n", path, d.IsDir(), fin.ModTime())
		if !d.IsDir() {

			f, err := os.Open(filepath.Join(cfg.InputPath, path))
			if err != nil {
				return err
			}
			defer f.Close()

			meta := map[string]string{
				"metaMtime": fin.ModTime().Format(time.RFC3339Nano),
			}

			input := &s3.PutObjectInput{
				Bucket:      aws.String(cfg.Bucket),
				Key:         aws.String(filepath.Join(cfg.Prefix, path)),
				Body:        f,
				Metadata:    meta,
				ContentType: aws.String(mime.TypeByExtension(filepath.Ext(path))),
			}

			res, err := client.PutObject(ctx, input)
			if err != nil {
				return err
			}

			log.Info().Str("path", path).Str("ETag", aws.StringValue(res.ETag)).Str("VersionId", aws.StringValue(res.VersionId)).Msg("object uploaded")
		}

		return nil
	})
	if err != nil {
		log.Fatal().Err(err).Msg("failed to walk path")
	}

}