code: func (wfe *WebFrontEndImpl) Nonce(
  	ctx context.Context,
  	logEvent *web.RequestEvent,
  	response http.ResponseWriter,
  	request *http.Request) {
  	statusCode := http.StatusNoContent
  	// The ACME specification says GET requets should receive http.StatusNoContent
  	// and HEAD requests should receive http.StatusOK. We gate this with the
  	// HeadNonceStatusOK feature flag because it may break clients that are
  	// programmed to expect StatusOK.
  	if features.Enabled(features.HeadNonceStatusOK) && request.Method == "HEAD" {
  		statusCode = http.StatusOK
  	}
  	response.WriteHeader(statusCode)
  }
docs: // Nonce is an endpoint for getting a fresh nonce with an HTTP GET or HEAD
  // request. This endpoint only returns a status code header - the `HandleFunc`
  // wrapper ensures that a nonce is written in the correct response header.