CouchbaseError: Client-Side timeout exceeded for operation. Inspect network conditions or increase the timeout

I am just running the code(ottoman-labs , CB130n) in training course example.

“CouchbaseError: Client-Side timeout exceeded for operation. Inspect network conditions or increase the timeout”

I cannot insert data… Why this happens ?
I even put some throttle(SetTimeout)

CouchServer 6.0.1 build 2037 , NodeSDK 2.6.4

'use strict'

var fs = require('fs')
var async = require('async')
var ottoman = require('ottoman')
var models = require('./models')

function sleep(ms) {
	return new Promise((resolve) => setTimeout(resolve, ms))
}

fs.readdir('docs/', function(err, files) {
	if (err) throw err

	console.log('Loading documents...')

	// Filter out only the .JSON files
	files = files.filter(function(file) {
		if (file.substr(file.length - 4) != 'json') {
			return false
		}
		return true
	})

	// Read all the document files
	async.map(
		files,
		function(file, callback) {
			fs.readFile('docs/' + file, function(err, buffer) {
				if (err) return callback(err)
				callback(null, JSON.parse(buffer))
			})
		},
		function(err, docs) {
			if (err) throw err

			console.log('Loaded all documents to memory')

			var countryDatas = []
			var customerDatas = []
			for (var i = 0; i < docs.length; ++i) {
				if (docs[i].type == 'country') {
					countryDatas.push(docs[i])
				} else if (docs[i].type == 'customer') {
					customerDatas.push(docs[i])
				}
			}

			console.log('Storing countries...')

			// Insert all the countries
			async.map(
				countryDatas,
				function(countryData, callback) {
					// Drop the original modelling fields
					delete countryData.type
					delete countryData.id

					// Create the country
          models.Country.create(countryData, callback)
          setTimeout(function() {
            console.log('setTimeOut')
          }, 1000)
				},
				function(err, countries) {
					if (err) throw err

					console.log('All countries stored')

					var countryMap = {}
					for (var i = 0; i < countries.length; ++i) {
						countryMap[countries[i].countryCode] = countries[i]
					}

					console.log('Storing customers...')

					// Insert all the Customers
					async.map(
						customerDatas,
						function(customerData, callback) {
							// Drop the original modelling fields
							delete customerData.type
							delete customerData.id

							// Map the customers country code to an actual country object
							customerData.billingAddress.country = countryMap[customerData.billingAddress.country]

							// Create the customer
							models.Customer.create(customerData, callback)
							setTimeout(function() {
                console.log('setTimeOut')
              }, 1000)
						},
						function(err, customers) {
							if (err) throw err

							console.log('All customers stored')
							process.exit(0)
						}
					)
				}
			)
		}
	)
})

I am having this same issue with the following versions:
“dependencies”: {
“async”: “^3.2.0”,
“body-parser”: “^1.19.0”,
“couchbase”: “^3.0.1”,
“express”: “^4.17.1”,
“node-uuid”: “^1.4.8”,
“ottoman”: “^1.0.6”,
“sync”: “^0.2.5”