Trying to interact with ganache-cli fork through script

Question

const {ChainId, Fetcher, WETH, Route, Trade, TokenAmount, TradeType, Percent} = require ('@uniswap/sdk');
const ethers = require('ethers');

const chainId = ChainId.MAINNET;

how would I specify it to be the locally forked ganache chain?

tried this:

const Web3 = require('web3');
const web3 = new Web3(`http://localhost:8545`);

const tokenAddress = '0x6B175474E89094C44Da98b954EedeAC495271d0F';

const init = async ()=> {
  const chainId = await web3.eth.getChainId();
...

following error is shown:

/Users/GreyShadow/node_modules/@ethersproject/logger/lib/index.js:179
        var error = new Error(message);
                    ^

Error: unsupported getDefaultProvider network (operation="getDefaultProvider", network={"chainId":1337,"name":"unknown"}, code=NETWORK_ERROR, version=providers/5.0.17)

Help is much appreciated