an class="keyword">bool</span>
<span class="identifier">is_upgrade</span><span class="special">(</span>
    <span class="identifier">beast</span><span class="special">::</span><span class="identifier">http</span><span class="special">::</span><span class="identifier">header</span><span class="special">&lt;</span> <span class="keyword">true</span><span class="special">,</span> <span class="identifier">http</span><span class="special">::</span><span class="identifier">basic_fields</span><span class="special">