code: func NewHTTPReadSeeker(client *http.Client, url string, errorHandler func(*http.Response) error) ReadSeekCloser {
  	return &httpReadSeeker{
  		client:       client,
  		url:          url,
  		errorHandler: errorHandler,
  	}
  }
docs: // NewHTTPReadSeeker handles reading from an HTTP endpoint using a GET
  // request. When seeking and starting a read from a non-zero offset
  // the a "Range" header will be added which sets the offset.
  // TODO(dmcgowan): Move this into a separate utility package