span class="identifier">string</span> <span class="identifier">chunk</span><span class="special">;</span>

    <span class="comment">// Declare our chunk header callback  This is invoked</span>
    <span class="comment">// after each chunk header and also after the last chunk.</span>
    <span class="keyword">auto</span> <span class="identifier">header_cb</span> <span class="special">=</span>
    <span class="special">[&amp;](</span><span class="identifier">std</span><span class="special">::</span><span cla