browser里面第7行输出的结果里面有"registry=RegistryFileName"，但是server里面第4行输出空……

browser

    $('#importFile').on('click', function(event) {
        var $this = $(this);
        var $registryFile = $('#registryFile');
        event.preventDefault();
        $.ajax({
            beforeSend: function(jqXHR, settings) {
                console.log(settings);
                $registryFile.parent('.form-group').removeClass('has-error');
                $registryFile.next('.help-block').text('Importing... Please wait...');
                $this.prop('disabled', true);
                $registryFile.prop('disabled', true);
            },
            url: 'import',
            type: 'POST',
            dataType: 'json',
            data: {registry: $registryFile.val()}
        }).done(function(data, textStatus, jqXHR) {
            if (data.err) {
                $registryFile.parent('.form-group').addClass('has-error');
                $registryFile.next('.help-block').text(data.err);
                $this.prop('disabled', false);
                $registryFile.prop('disabled', false);
            } else {
                location.reload(true);
            }
        }).fail(function(jqXHR, textStatus, errorThrown) {
            attrAddModal.modal('hide');
            $('#errorModal p').text(textStatus);
            errorModal.modal('show');
        });
    });

server

func (h *importHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	var invalid error
	fname := string(r.PostFormValue("registry"))
	fmt.Println(fname)
	if _, err := os.Stat(fname); os.IsNotExist(err) {
		invalid = errors.New("File does not exists!")
	} else {
		f, err := os.Open(fname)
		if err != nil {
			panic(err)
		}
		defer f.Close()
		enc := unicode.UTF16(unicode.LittleEndian, unicode.ExpectBOM)
		tf := enc.NewDecoder()
		reader := transform.NewReader(f, tf)
		processRegistry(h.collection, reader)
	}
	response, err := json.Marshal(bson.M{"err": invalid.Error()})
	if err != nil {
		panic(err)
	}
	w.Header().Set("Content-Type", "application/json")
	w.Write(response)
}