jose.go
func Sign(payload string, signingAlg string, key interface{}, options ...func(*JoseConfig)) (token string, err error) {
	return SignBytes([]byte(payload), signingAlg, key, options...)
}
func Sign(payload string, signingAlg string, key interface{}, options ...func(*JoseConfig)) (token string, err error) {
	return SignBytes([]byte(payload), signingAlg, key, options...)
}
// Sign produces signed JWT token given arbitrary string payload, signature algorithm to use (see constants for list of supported algs), signing key and extra options (see option functions)
// Signing key is of different type for different signing alg, see specific
// signing alg implementation documentation.
//
// It returns 3 parts signed JWT token as string and not nil error if something went wrong.