Parse Content Disposition header in GO - http

Question

I am trying to retrieve the filename from this http writer for testing purposes.
On the server I have:
func servefile(w http.ResponseWriter, r *http.Request ) {
...
// file.Name() is randomized with os.CreateTemp(dir, temp+"*"+ext) above
w.Header().Set("Content-Disposition", "attachment; filename="+file.Name())
w.Header().Set("Content-Type", "application/octet-stream")
http.ServeFile(w, r, file.Name()+".xyz") // serve file to user to download
...
}
*I put .xyz as a place holder for this demonstration
I am testing this function programatically with Go and I want to access the filename to able to save it in a variable in the client code.
I have looked at this post How can I parse the Content-Disposition header to retrieve the filename property? , but I have not gotten it to work. I have no clue what the filename is on the client side so I don't know how to reference it specifically. I know my code on the server side works, because when I send a request (through the browser) to this endpoint/function, the "Downloads" popup shows the file download progress with the name of the file.
EDIT** This is the client code I am calling it from:
func TestGetFile(t *testing.T) {
...
cid := "some string"
// requestfile() creates, executes, and returns an httptest.ResponseRecorder to the requestFile endpoint
reqfileRespRecorder := requestfile()
// createTmpFile creates a new file out of the contents recieved in requestfile()
filePath := "/tmp/temp.xyz"
file := createTmpFile(reqfileRespRecorder , filePath)
// CreateWriter() - writes file contents to body of multipart.Writer
w, body := createWriter(file)
// Create request to postRecord endpoint
req, err := http.NewRequest("POST", "/PostRecord?CID="+cid, body)
check(err)
req.Header.Add("Content-Type", w.FormDataContentType())
// execute request to PostRecord endpoint. returns an httptest.ResponseRecorder
respRecorder := executeRequest(PostRecord, req)
disposition, params, err := mime.ParseMediaType(`Content-Disposition`)
...
}

Answer 1

Based on #BaytaDarrell's comment. It dawned on me that I could print out the responses. That helped me realize that I was trying to find the content-disposition after the wrong request/response. The linked post still didn't help, but I got my code working like this:
func TestGetFile(t *testing.T) {
...
cid := "some string"
// requestfile() creates, executes, and returns an httptest.ResponseRecorder to the requestFile endpoint
reqfileRespRecorder := requestfile()
disp := reqfileRespRecorder.Header().Get("Content-Disposition")
line := strings.Split(disp, "=")
filename := line[1]
fmt.Println("filename: ", filename)
// createTmpFile creates a new file out of the contents recieved in requestfile()
filePath := "/tmp/temp.xyz"
file := createTmpFile(reqfileRespRecorder , filePath)
// CreateWriter() - writes file contents to body of multipart.Writer
w, body := createWriter(file)
...
}
Their comment realized I should re-look at the httptest package documentation. Here I found the Header() function and that I can use it to look at the header with Get().
This line reqfileRespRecorder.Header().Get("Content-Disposition") returns attachment; filename=temp37bf73gd.xyz and to store the filename in a variable I split on =.