aws s3 S3AuthorizedUpload

gistfile1.go

// Server
func S3signatureGeneration() string{
	now := time.Now().UTC()
	policyDate, dateStamp := now.Format(ISO8601BasicFormat), now.Format(ISO8601BasicFormatShort)
	expirationTime := now.Add(uploadValidity + 5*time.Minute).Format(ISO8601)

	allowedPath := "test/"
	credential := XAMZCredential(awsAccessKeyID, dateStamp, awsRegion)
	str := "{ \"expiration\": \"%s\",\"conditions\": [{\"bucket\": \"%s\"},[\"starts-with\", \"$key\", \"%s\"],{\"acl\": \"%s\"},{\"x-amz-credential\": \"%s\"},{\"x-amz-algorithm\": \"AWS4-HMAC-SHA256\"},{\"x-amz-date\": \"%s\" }]}"
	finalStr := fmt.Sprintf(str, expirationTime, awsBucket, allowedPath, acl, credential, policyDate)

        base64Policy := base64.StdEncoding.EncodeToString([]byte(finalStr))

	SigningKey := getSignatureKey(awsSecretAccessKey, dateStamp, awsRegion, "s3")
	S3Signature := hex.EncodeToString(hmacSHA256(SigningKey, []byte(base64Policy)))

        return S3Signature
}

//client 
func Upload(s3Filename string, config *Config){
fields := [][]string{
		[]string{"key", config.Path + s3Filename},
		[]string{"acl", config.ACL},
		[]string{"X-Amz-Credential", config.Credential},
		[]string{"X-Amz-Algorithm", "AWS4-HMAC-SHA256"},
		[]string{"X-Amz-Date", config.PolicyDate},
		[]string{"Policy", config.Base64Policy},
		[]string{"X-Amz-Signature", config.S3Signature},
		[]string{"file", "{\"test\": \"a\"}"},
	}

  S3AuthorizedUpload(fmt.Sprintf("http://%s.s3.amazonaws.com", config.AwsBucket), fields)
}

func S3AuthorizedUpload(url string, fields [][]string) error {
	var b bytes.Buffer
	w := multipart.NewWriter(&b)
	for _, value := range fields {
		fw, err := w.CreateFormField(value[0])
		if err != nil {
			return err
		}
		if _, err := fw.Write([]byte(value[1])); err != nil {
			return err
		}
	}
	w.Close()

	req, err := http.NewRequest("POST", url, &b)
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", w.FormDataContentType())

	client := &http.Client{}
	res, err := client.Do(req)
	if err != nil {
		return err
	}
	if res.StatusCode != http.StatusOK {
		err = fmt.Errorf("bad status: %s", res.Status)
	}

	if response, err := ioutil.ReadAll(res.Body); err != nil {
		return err
	} else {
		log.Println(string(response))
	}

	return nil
}