code: func (d Data) GetFileBytes(key string) ([]byte, error) {
  	fileHeader, found := d.Files[key]
  	if !found {
  		return nil, nil
  	} else {
  		file, err := fileHeader.Open()
  		if err != nil {
  			return nil, err
  		}
  		return ioutil.ReadAll(file)
  	}
  }
docs: // GetFileBytes returns the body of the file associated with key. If there is no
  // file associated with key, it returns nil (not an error). It may return an error if
  // there was a problem reading the file. If you need to know whether or not the file
  // exists (i.e. whether it was provided in the request), use the FileExists method.