main.go

package main

import (
	"context"
	"fmt"
	"net/http"
	"net/url"
	"strconv"
	"time"

	v4 "github.com/aws/aws-sdk-go-v2/aws/signer/v4"
	"github.com/aws/aws-sdk-go-v2/config"
)

func main() {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	if err := _main(ctx); err != nil {
		panic(err)
	}

}

func _main(ctx context.Context) error {
	cfg, err := config.LoadDefaultConfig(ctx, config.WithRegion("ap-northeast-1"))
	if err != nil {
		return err
	}

	signer := v4.NewSigner(func(signer *v4.SignerOptions) {
		signer.DisableURIPathEscaping = true
	})
	cred, err := cfg.Credentials.Retrieve(ctx)
	if err != nil {
		return err
	}

	expire := 1 * time.Minute
	expireStr := strconv.FormatInt(int64(expire/time.Second), 10)

	originalURL, err := url.Parse(
		fmt.Sprintf(
			"https://%s.s3-%s.amazonaws.com/%s",
			"my-bucket",
			cfg.Region,
			"filename",
		),
	)
	if err != nil {
		return err
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, originalURL.String(), nil)
	if err != nil {
		return err
	}
	req.Header.Set("X-Amz-Expires", expireStr)

	now := time.Now()

	if err := signer.SignHTTP(ctx, cred, req, "UNSIGNED-PAYLOAD", "s3", cfg.Region, now); err != nil {
		return err
	}

	s := `
curl -H "Authorization: %s" \
-H 'X-Amz-Content-Sha256: %s' \
-H 'X-Amz-Expires: %s' \
-H 'X-Amz-Date: %s' \
-H 'X-Amz-Security-Token: %s' \
%s
`
	fmt.Println(fmt.Sprintf(
		s,
		req.Header.Get("Authorization"),
		"UNSIGNED-PAYLOAD",
		req.Header.Get("X-Amz-Expires"),
		req.Header.Get("X-Amz-Date"),
		req.Header.Get("X-Amz-Security-Token"),
		originalURL,
	))
	return nil
}