<nav class="navbar navbar-expand-lg w-100">

      <div class="container-fluid">

        <a class="navbar-brand" href="#">Brand</a>

        <div class="input-group">

          <span class="input-group-text"><i class="fas fa-search"></i></span>

          <div id="autocomplete" class="form autocomplete flex-fill">

            <input type="search" class="form-control" placeholder="Search" aria-label="Search"/>

          </div>

        </div>

      </div>

    </nav>