Golang beego输出到csv文件会将数据转储到浏览器，但不会转储到文件

I tried to ouput some data to csv file in golang beego framework, here is my code

records := make([][]string,len(devicesData))

for k,v := range devicesData{
    records[k] = []string{v.Fields.Country,v.Fields.Imei[0],v.Fields.Number[0]}
}

writer := csv.NewWriter(this.Controller.Ctx.ResponseWriter)
for _, record := range records {
    err := writer.Write(record)
    if err != nil {
        fmt.Println("Error:", err)
        return
    }
}

this.Ctx.Output.Header("Content-Type", "application/csv")
this.Ctx.Output.Header("Content-Disposition", "attachment; filename=MyVerySpecial.csv")

    writer.Flush()

However, it only shows the record data in browser, it cannot download the file. I have some loging controller and filter function before this download file controller, I do not whether it is affected. What's wrong with my code? Thanks