type SigningMethodHMAC … var SigningMethodHS256 … var SigningMethodHS384 … var SigningMethodHS512 … var ErrSignatureInvalid … func init() { … } func (m *SigningMethodHMAC) Alg() string { … } // Verify implements token verification for the SigningMethod. Returns nil if the signature is valid. func (m *SigningMethodHMAC) Verify(signingString, signature string, key interface{ … } // Sign implements token signing for the SigningMethod. // Key must be []byte func (m *SigningMethodHMAC) Sign(signingString string, key interface{ … }