How to Create Multiple Select Field in Widget ServiceNow

<label class="ng-binding" for="domain style="padding: 0px 0px 0px 0px;display: block;">Domain Instance<span class="setRedColor">*</span></label>
 <select class="form-control heightselect dropDownWidth"style="border: 1px solid #F5F2F7; background-color: #F5F2F7 !important;border-radius: 17px !important;" ng-model="domain"
id="domain_instance" ng-change="c.checkdomain()" multiple>
 <option value="" disabled selected>Select</option>
  <option value="Workingcode Production ">Workingcode Production </option>
  <option value="Workingcode test">Workingcode test</option>
   <option value="Workingcode dev">Workingcode dev</option>
    </select>