I am looking for a solution to create and input like this one in bootstrap 4

I am using font awesome and this is the code that I use
<div class="input-group">
<label class="control-label">Username</label>
<input type="text" class="form-control" placeholder="Username" />
<span>
<i class="fa fa-user-circle-o" aria-hidden="true"></i>
</span>
</div>
but i get the image out of the input Any help please https://jsfiddle.net/5db2ho62/