I have a CasperJS process that loads some page and then it needs to call a go-process to analyze the page and to decide what page should be loaded next. go-process takes a while to execute. My problem is that CasperJS doesn't wait for the go-process to complete and exits. 

```
casper.then(function(){
  var p = cp.execFile('/path/parse', [], {}, function(error, stdout, stderr) {
    console.log(stdout);
  });

});

```

How can I wait for my child process to complete?