message: Can't use optional chaining in node12
diff: @@ -33,7 +33,7 @@ export default class GraphQLClient {
  // GraphQL typically returns a list of errors
  errors.forEach((err) => {
  // Throw an error to retry the query if it's safe to do so, otherwise bail
  - if (err.extensions?.code === RETRYABLE_ERROR_CODE) throw err;
  + if (err.extensions && err.extensions.code === RETRYABLE_ERROR_CODE) throw err;
  // eslint-disable-next-line no-param-reassign
  err.name = err.name || 'GraphQLError';
  