code: func (k *Kite) PreHandle(handler Handler) {
  	k.preHandlers = append(k.preHandlers, handler)
  }
docs: // PreHandle registers an handler which is executed before a kite.Handler
  // method is executed. Calling PreHandle multiple times registers multiple
  // handlers. A non-error return triggers the execution of the next handler. The
  // execution order is FIFO.