text: var jwt = require('jsonwebtoken');
  
  module.exports.issueToken = function(payload, options) {
    var token = jwt.sign(payload, process.env.TOKEN_SECRET || "secret zin", options);
    return token;   // jwt.token_secret
  };
  
  module.exports.verifyToken = function(token, callback) {
    return jwt.verify(token, process.env.TOKEN_SECRET || "secret zin", {}, callback);
  };