How to generate a web3 object?

Question

The following example does not hang.

$ cat main.js 
#!/usr/bin/env node
// vim: set noexpandtab tabstop=2:

const Web3 = require('web3');
const web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
web3.eth.getAccounts()
    .then((accounts) => {
        console.log(accounts);
    })

But the following code hangs. Does anybody know why?

$ cat main.js 
#!/usr/bin/env node
// vim: set noexpandtab tabstop=2:

const web3 = new (require('web3'))("ws://localhost:8545");
web3.eth.getAccounts()
    .then((accounts) => {
        console.log(accounts);
    })