// prefixed by 'proto='. The match is case-insensitive.
	protoRegex = regexp.MustCompile(`(?i)^(;|,| )+(?:proto=)(https|http)`)
)

// GetSourceScheme retrieves the scheme from the X-Forwarded-Proto and RFC7239
// Forwarded headers (in that order).
func GetSourceScheme(r *http.Request) string {
	var scheme string

	// Retrieve the scheme from X-Forwarded-Proto.
	if proto := r.Header.Get(xForwardedProto); proto != "" {