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: customerdemographic.xo.go
    path of file: ./repos/xo/_examples/northwind/mysql
    
    the code of the file until where you have to start completion: package mysql

// Code generated by xo. DO NOT EDIT.

import (
	"context"
	"database/sql"
)

// CustomerDemographic represents a row from 'northwind.customer_demographics'.
type CustomerDemographic struct {
	CustomerTypeID string         `json:"customer_type_id"` // customer_type_id
	CustomerDesc   sql.NullString `json:"customer_desc"`    // customer_desc
	// 
    
func CustomerDemographicByCustomerTypeID(ctx context.Context, db DB, customerTypeID string) (*CustomerDemographic, error) {
	// query
	const sqlstr = `SELECT ` +
		`customer_type_id, customer_desc ` +
		`FROM northwind.customer_demographics ` +
		`WHERE customer_type_id = ?`
	// run
	logf(sqlstr, customerTypeID)
	cd := CustomerDemographic{
		_exists: true,
	}
	if err := db.QueryRowContext(ctx, sqlstr, customerTypeID).Scan(&cd.CustomerTypeID, &cd.CustomerDesc); err != nil {
		return nil, logerror(err)
	}
	return &cd, nil
}