【Node.js】How to fix the error "fetch is not defined"

Version of node.js...v14.15.4

PROBLEM

When I executed query in Apollo Server, I encountered this error message from the server.

"errors": [
    {
      "message": "fetch is not defined",
      "locations": [
        {
          "line": 3,
          "column": 1
        }........

What does this mean? "fetch" is a method that handles request and response in asynchronous communication. Looks like this method is causing this error message.

const resolvers = {
    Query: {
        singlePokemon:async(parent, args) => {
      let res = await fetch(`https://pokeapi.co/api/v2/pokemon/${args.id}`);

SOLUTION

The version of Node before 18 does not have the fetch API. So, you need to install an external module.
https://www.npmjs.com/package/node-fetch

npm install node-fetch