How to make a synchronous query (blocking call) with node-postgres?

The only way to synchronize calls is to nest them in callbacks:

function init() {
  pg.connect('tcp://user@host/db', function(err, client, done) {
    client.query("SELECT column FROM table", function(err, result) {
      // check some things...
      client.query("SELECT column FROM other_table", function(err, result) {
        // check some other things...
        main(); // proceed with flow...
      }
    });
  }
}

function main() {
  // main logic
}

This can be a pain, and would be trivial in some other languages, but it is the nature of the beast.