default_context.go
func (d *DefaultContext) File(name string) (binding.File, error) {
	req := d.Request()
	if err := req.ParseMultipartForm(5 * 1024 * 1024); err != nil {
		return binding.File{}, err
	}
	f, h, err := req.FormFile(name)
	bf := binding.File{
		File:       f,
		FileHeader: h,
	}
	if err != nil {
		return bf, err
	}
	return bf, nil
}
func (d *DefaultContext) File(name string) (binding.File, error) {
	req := d.Request()
	if err := req.ParseMultipartForm(5 * 1024 * 1024); err != nil {
		return binding.File{}, err
	}
	f, h, err := req.FormFile(name)
	bf := binding.File{
		File:       f,
		FileHeader: h,
	}
	if err != nil {
		return bf, err
	}
	return bf, nil
}
// File returns an uploaded file by name, or an error