if idx > 0 {
				buf.WriteByte(',')
			}
			buf.WriteString(signV4TrimAll(v))
		}
		buf.WriteByte('\n')
	}
	return buf.String()
}

// getSignedHeaders generate a string i.e alphabetically sorted, semicolon-separated list of lowercase request header names
func getSignedHeaders(signedHeaders http.Header) string {
	var headers []string
	for k := range signedHeaders {
		headers = append(headers, strings.ToLower(k))
	}