How to make an input field with a button on bootstrap?

Question

Bootstrap

I know how to make an input field with an additional icon

<div class="input-group margin-bottom-sm">
  <span class="input-group-addon"><i class="fa fa-envelope-o fa-fw"></i></span>
  <input class="form-control" type="text" placeholder="Email address">
</div>

But how to make this icon a button?
UPDATE:
I asked myself - I answer myself. More or less like this:

<div class="input-group">
        <span class="input-group-btn">
          <button class="btn btn-default" type="button">Вперед!</button>
        </span>
        <input type="text" class="form-control">
</div>