Use try..catch or promise error won't be catched

[rofrol]

for example this returns error:

(node:2919) UnhandledPromiseRejectionWarning: ReferenceError: query is not defined
    at file:///Users/romanfrolow/personal_projects/fetch-graphql-schema-custom/index.mjs:22:13
    at <anonymous>
(node:2919) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:2919) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

for code:

import fs from 'fs';
import path from 'path';
import fetch from 'node-fetch';
import { buildClientSchema, printSchema } from 'graphql/utilities';

import expose from './expose';
const {__dirname} = expose;

const custom = process.argv[2] === '--custom';

(async () => {
  try {
    const { introspectionQuery: query } = await import(custom ? './introspection-query' : 'graphql/utilities');
      } catch (error) {
    console.error(error);
  }

  fetch('http://127.0.0.1:8080/graphql2', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(custom
        ? { query, variables: { includeDeprecated: true } }
        : { query }
      ),
  })
  .catch(error => console.error('BAD', error))
  .then(result => {
    if (result.errors) {
      console.error(
        'ERROR introspecting schema: ',
        JSON.stringify(result.errors, null, 2)
      );
    } else {
      result.json()
      .catch(error => console.error('BAD', error))
      .then(json => {
        fs.writeFileSync(
          path.join(__dirname, './schema.json'),
          JSON.stringify(json, null, 2)
        );
        fs.writeFileSync(
          path.join(__dirname, './schema.graphql'),
          printSchema(buildClientSchema(json.data))
        );
      });
    }
  });
})()

instead of

{ FetchError: invalid json response body at http://127.0.0.1:8080/graphql2 reason: Unexpected end of JSON input
    at /Users/romanfrolow/personal_projects/fetch-graphql-schema-custom/node_modules/node-fetch/lib/index.js:254:32
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:118:7)
  message: 'invalid json response body at http://127.0.0.1:8080/graphql2 reason: Unexpected end of JSON input',
  type: 'invalid-json' }

with the version using try..catch https://github.com/rofrol/fetch-graphql-schema-custom