node.js - Winstonjs does not log any exceptions? -

i using winston log information in koajs application. have tried make default logger log unhandled exceptions following documentation here:

but reason unhandled exceptions being logged if thrown index.js file. throwing exception 1 of routes not result in winston logging exception?

edit:

here code:

let winston = require('winston');  let cassandra = require('cassandra-driver'); let winstoncassandra = require('../lib/winston_cassandra/index'); let config = require("../config/config");  let authprovider = new cassandra.auth.plaintextauthprovider(config.cassandra.username, config.cassandra.password);  let defaultloggeroptions = {   table: "logs",   level: "debug",   consistency: cassandra.types.consistencies.one,   contactpoints: config.cassandra.contactpoints,   keyspace: config.cassandra.keyspace,   authprovider: authprovider,   name: "cassandradefaultlog" };  let errorloggeroptions = {   table: "log_exceptions",   level: "error",   consistency: cassandra.types.consistencies.one,   contactpoints: config.cassandra.contactpoints,   keyspace: config.cassandra.keyspace,   authprovider: authprovider,   handleexceptions: true,   name: "cassandraerrorlog" };  winston.add(winstoncassandra, defaultloggeroptions); winston.add(winstoncassandra, errorloggeroptions);  if(config.env != 'development') {   winston.remove(winston.transports.console); }