code: function(key) {
          var value = this.loadVar(key);
          if (typeof(value) =='undefined') {
              exitProcess('the value of ' + key + ' is necessary , but now is undefined', this.alarm);
              return false;
          }
          return value;
      }
docs: Get value by key, the value must be exist, otherwise the process will exit.
  
  @param {KeyItem} key
  @returns {String|Object}