How do you bypass buttons by pressing enter in a textbox?

I have the code for a button that takes the input box text and turns it into a google ssearch

var addPluses = function():Void {
 var inp:String = input_txt.text;
 //split the input string on the spaces - this forms an array
 var spl:Array = inp.split(" ");
 // join the array back together w/ "+"
 var finish:String = spl.join("+");
 getURL("" + finish + "&meta=", "_self")
go_btn.onRelease = function():Void {

so my question is how do i get that now so when you type the search and hit enter it eliminates the need to press the search button?

Cheers for any help