cmd/jwt/main.go
func getAlgFromKeyData(pem pemutil.Store) (jwt.Algorithm, error) {
	for _, v := range pem {
		// loop over crypto primitives in pemstore, and do type assertion. if
		// ecdsa.{PublicKey,PrivateKey} found, then use corresponding ESXXX as
		// algo. if rsa, then use DefaultRSAAlgorithm. if []byte, then use
		// DefaultHMACAlgorithm.
		switch k := v.(type) {
		case []byte:
			return jwt.HS512, nil

		case *ecdsa.PrivateKey:
			return getSuitableAlgFromCurve(k.Curve)

		case *ecdsa.PublicKey:
			return getSuitableAlgFromCurve(k.Curve)

		case *rsa.PrivateKey:
			return jwt.PS512, nil

		case *rsa.PublicKey:
			return jwt.PS512, nil
		}
	}

	return jwt.NONE, errors.New("cannot determine key type")
}
func getAlgFromKeyData(pem pemutil.Store) (jwt.Algorithm, error) {
	for _, v := range pem {
		// loop over crypto primitives in pemstore, and do type assertion. if
		// ecdsa.{PublicKey,PrivateKey} found, then use corresponding ESXXX as
		// algo. if rsa, then use DefaultRSAAlgorithm. if []byte, then use
		// DefaultHMACAlgorithm.
		switch k := v.(type) {
		case []byte:
			return jwt.HS512, nil

		case *ecdsa.PrivateKey:
			return getSuitableAlgFromCurve(k.Curve)

		case *ecdsa.PublicKey:
			return getSuitableAlgFromCurve(k.Curve)

		case *rsa.PrivateKey:
			return jwt.PS512, nil

		case *rsa.PublicKey:
			return jwt.PS512, nil
		}
	}

	return jwt.NONE, errors.New("cannot determine key type")
}
// getAlgFromKeyData determines the best jwt.Algorithm suitable based on the
// set of given crypto primitives in pem.