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{
You should always set response headers first and only after that start writing any data to the output. I know you called writer.Flush()
after setting header fields, but that is no guarantee whatsoever that data will not be flushed or sent before that - which will imply default headers being sent. After this no additional headers can be sent or changed.
Also the proper mime type for CSV is text/csv
not application/csv
(rfc4180).
Also the headers are more like a "proposal" to the browser. That's one thing you suggest the response is a file to be saved, but from the server side you can't force the browser to really save the response to a file and not display it.
See rfc1806, rfc2183 and rfc6266 for more details about the "Content-Disposition"
header field. Basically it communicates presentation information.
The Content-Disposition response header field is used to convey additional information about how to process the response payload, and also can be used to attach additional metadata, such as the filename to use when saving the response payload locally.