Take an input float as left. Then take the button and float it right. You can clearfix class when you take more than one to distance.
<input style="width:65%;float:left"class="btn btn-primary" type="text" name="name">
<div style="width:8%;float:left"> </div>
<button class="btn btn-default" type="button">Go!</button>
<div class="clearfix" style="margin-bottom:10px"> </div>