You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: customerService.go
    path of file: ./repos/learning/golang/source_code/Go语言核心编程代码/customer/service
    
    the code of the file until where you have to start completion: package service

import (
	_ "fmt"
	"go_code/customer/model"
)

type CustomerService struct {
	//定义一个客户切片,可以存放客户信息
	customers []*model.Customer
	//定义客户的实际个数
	customerNum int
}

//先创建一个Customer对象
    
func (this *CustomerService) Add(customer *model.Customer) bool {

	this.customerNum++
	//这时我们可以这个customer一个id
	customer.Id = this.customerNum
	this.customers = append(this.customers, customer)
	
	return true
	
}