Node asyn I/O with callback after I/O returns

asyncIO.js

var http = require('http');
var bl = require('bl');

// file path is from enviroment variable passed in through CLI
var url = process.argv[2];

var consolidated = '';

var callback = function(data) {
    consolidated += data;
};

// http get request takes a callback with signature callback(response)
http.get(url, function(response) {
    // set encoding to UTF to print string rather than buffer object
    //response.setEncoding('utf8');
    // error callback
    response.on('error', function(err) {
        console.error("Error: ${err}");
    });
    // data call back
    // Response is a stream object, which will continuously emit events
    // you can trigger specific call backs on specific events from Response

    response.pipe(bl(function(err, data) {
        if (err) {
            console.err(err);
        }
        data = data.toString();
        console.log(data.length);
        console.log(data);
    }));
}).on('error', function(err) {
    console.error("There was an error submitting the http request.");
});