You can add the font-awesome icon with custom CSS (content property):
Just use <i class="fa"></i> and
[data-toggle="collapse"] .fa:before {   
  content: "\f139";
}
[data-toggle="collapse"].collapsed .fa:before {
  content: "\f13a";
}
Example in codepen
Solution with no FontAwesome unicode and no JavaScript:
Example:
HTML:
<a data-toggle="collapse" href="#collapseNEWS" aria-expanded="true" aria-controls="collapseNEWS">
    <i class="fa fa-chevron-circle-up"></i>
    <i class="fa fa-chevron-circle-down"></i>
</a>
CSS:
[aria-expanded="true"] .fa-chevron-circle-up, 
[aria-expanded="false"] .fa-chevron-circle-down {
    display:none;
}
Using Rails and Bootstrap 4 with Fontawesome 5.5
This didn't quite work for me, It was flipping it on the re-close. I had to add another state control:
[data-toggle="collapse"] .fas:before {  
  content: "\f055";
}
[aria-expanded="true"] .fas:before {  
  content: "\f056";
}
[data-toggle="collapse"].collapsed .fas:before {
  content: "\f055";
}
You can add toggleClass() to onclick event of <a></a> element and additional class fa-rotate-180 for element of Font Awesome icon.
fa-rotate-180- standard class from Font Awesome.
<a href='' onclick="$('#collapsed-chevron').toggleClass('fa-rotate-180')">
   <i class="fa fa-chevron-circle-up" id="collapsed-chevron"></i>
   Link Text
</a>
For SASS version of FontAwesome 5, use the fa-content() mixin
HTML:
<i class="fas"></i>
SASS:
[data-toggle="collapse"] i.#{$fa-css-prefix}s:before {
  content: fa-content($fa-var-chevron-circle-down);
}
[data-toggle="collapse"].collapsed i.#{$fa-css-prefix}s:before {
  content: fa-content($fa-var-chevron-circle-right);
}
I prefer using chevron in a circle background
To extend this further - now using Bootstrap 4 Beta if it makes a difference:
This won't work when the initial state is collapsed - the icon will be reversed. Clicking the button through a cycle will fix it - but it'd be nice to have it right to begin with. The secret: add
class="collapsed"
to the toggling link(s). An example with a clickable text heading as well as the icon:
<div class="card-header d-flex justify-content-between" id="headingCollapse1">
    <div>
        <a class="collapsed" data-toggle="collapse" href="#collapse1" aria-expanded="false" aria-controls="collapse1">
            Card Header
        </a>
    </div>
    <div>
        <a data-toggle="collapse" class="collapsed btn btn-default btn-xs text-right" href="#collapse1" aria-label="Expand/Collapse Card 1" aria-expanded="false" role="button">
            <i class="fa" aria-hidden="true"></i>
            <span class="sr-only">Expand/Collapse Card 1</span>
        </a>
    </div>
</div>
<div id="collapse1" class="collapse" aria-labelledby="headingCollapse1">
    <div class="card-body">
        Here is some wonderful content that you can't see...until expanded!
    </div>
</div>
I also find the plus/minus symbols more intuitive - with arrows, I'm never quite sure if it means "current status is opened/closed" or "press this to open/close". Based on tree views, among others, I'm used to "+" means "closed/click to open", and "-" means "open/click to close". So while not directly part of the question I'll leave this for others to find (full credit to @tmg above for format - I just plugged in the "correct" characters):
[data-toggle="collapse"] i:before{
    content: "\f146";
}
[data-toggle="collapse"].collapsed i:before{
    content: "\f0fe";
}