code: func (a *Agent) FailTTL(checkID, note string) error {
  	return a.updateTTL(checkID, note, "fail")
  }
docs: // FailTTL is used to set a TTL check to the failing state.
  //
  // DEPRECATION NOTICE: This interface is deprecated in favor of UpdateTTL().
  // The client interface will be removed in 0.8 or changed to use
  // UpdateTTL()'s endpoint and the server endpoints will be removed in 0.9.