node-postgres: Connection intermittently made, rejects connection with password authentication failure notice

OSX 10.11.4 PG 9.4.8 Using pg module.

var pg = require('pg');
var conString = "postgres://postgres:REDACTED@localhost/testDb";

pg.connect(conString, function(err, client, done) {
  if(err) {
    return console.error('error fetching client from pool', err);
  }
  client.query('SELECT $1::int AS number', ['1'], function(err, result) {
    //call `done()` to release the client back to the pool 
    done();

    if(err) {
      return console.error('error running query', err);
    }
    console.log(result.rows[0].number);
    //output: 1 
  });
});

I get the following error:

error fetching client from pool { error: password authentication failed for user “postgres”

Then if I run this code with node - say - 10-15 times, it’ll work once out of those attempts.

I’ve reinstalled postgres and made sure the passwords match. I tried performing an alter user for the password. I tried killing all open connections with pg_terminate_backend(pid). Still fails. Any help would be appreciated. Everything was working with this prior to upgrading to El Capitan, is El Capitan not supported?