test.js

(function() {
  var pg;

  pg = require("pg");

  pg.connect("pg://postgres:thesecret@localhost/database", function(error, client) {
    if (error) {
      return console.log(error);
    } else {
      return client.query("CREATE TEMP TABLE users(id int, name varchar)", function(error, result) {
        if (error) {
          return console.log(error);
        } else {
          return client.query("INSERT INTO users(id, name) VALUES (0, 'foo') RETURNING id", function(error, results) {
            if (error) {
              return console.log(error);
            } else {
              return console.log(results);
            }
          });
        }
      });
    }
  });

}).call(this);

Curious, why do you return almost every expression?