"X-Amz-Algorithm":     signV4Algorithm,
				"X-Amz-Date":          now.Format(iso8601Format),
				"X-Amz-Expires":       "60",
				"X-Amz-Signature":     "badsignature",
				"X-Amz-SignedHeaders": "host;x-amz-content-sha256;x-amz-date",
				"X-Amz-Credential":    fmt.Sprintf(credentialTemplate, "Z7IXGOO6BZ0REAN1Q26I", now.Format(yyyymmdd), "us-west-1"),
			},
			region:   "us-west-1",

// extractSignedHeaders extract signed headers from Authorization header
func extractSignedHeaders(signedHeaders []string, r *http.Request) (http.Header, APIErrorCode) {
	reqHeaders := r.Header
	reqQueries := r.Form
	// find whether "host" is part of list of signed headers.
	// if not return ErrUnsignedHeaders. "host" is mandatory.
	if !slices.Contains(signedHeaders, "host") {
		return nil, ErrUnsignedHeaders
	}

	//  <HTTPMethod>\n
	//  <CanonicalURI>\n
	//  <CanonicalQueryString>\n
	//  <CanonicalHeaders>\n
	//  <SignedHeaders>\n
	//  <HashedPayload>
	//
	canonicalRequest := strings.Join([]string{
		req.Method,
		canonicalURI,
		req.URL.RawQuery,
		canonicalHeaders,
		signedHeaders,
		hashedPayload,
	}, "\n")

	// Get scope.
	scope := strings.Join([]string{
		currTime.Format(yyyymmdd),

	AmzContentSha256        = "X-Amz-Content-Sha256"
	AmzDate                 = "X-Amz-Date"
	AmzAlgorithm            = "X-Amz-Algorithm"
	AmzExpires              = "X-Amz-Expires"
	AmzSignedHeaders        = "X-Amz-SignedHeaders"
	AmzSignature            = "X-Amz-Signature"
	AmzCredential           = "X-Amz-Credential"
	AmzSecurityToken        = "X-Amz-Security-Token"
	AmzDecodedContentLength = "X-Amz-Decoded-Content-Length"

		Description:    "Signature header missing Signature field.",
		HTTPStatusCode: http.StatusBadRequest,
	},
	ErrMissingSignHeadersTag: {
		Code:           "InvalidArgument",
		Description:    "Signature header missing SignedHeaders field.",
		HTTPStatusCode: http.StatusBadRequest,
	},
	ErrMalformedExpires: {
		Code:           "AuthorizationQueryParametersError",
		Description:    "X-Amz-Expires should be a number",