code: func SignHTTPRequest(req *http.Request, region, service string, creds *credentials.Credentials, body io.ReadSeeker) error {
  	signer := v4.NewSigner(creds)
  	_, err := signer.Sign(req, body, service, region, time.Now())
  	if err != nil {
  		seelog.Warnf("Signing HTTP request failed: %v", err)
  		return errors.Wrap(err, "aws sdk http signer: failed to sign http request")
  	}
  	return nil
  }
docs: // SignHTTPRequest signs an http.Request struct with authv4 using the given region, service, and credentials.