sign method Null safety
Signs the JWT with the private key and returns the token.
Implementation
void sign() {
final payload = <String, dynamic>{
'iss': issuerId,
'exp': _createExpirationTimeAsUnixEpochTime(DateTime.now()),
'aud': audience,
};
final claims = JsonWebTokenClaims.fromJson(payload);
final builder = JsonWebSignatureBuilder()
..jsonContent = claims.toJson()
..addRecipient(
JsonWebKey.fromPem(privateKey, keyId: keyId),
algorithm: 'ES256',
);
_jws = builder.build();
_currentToken = _jws.toCompactSerialization();
}