el for="username" class="sr-only">请输入用户名</label>
    <input type="text" id="username" name="username" class="form-control" placeholder="用户名" required="true"
           autofocus="true" minlength="11" maxlength="11"/>
    <label for="password" class="sr-only">请输入密码</label>
    <input type="password" name="password" id="password" class="form-control" placeholder="密码" required="true"
           minlength="6" maxlength="16"/>
    <div class="checkbox mb-3" align="center">
       