how to disable input field in bootstrap 4 code example

Example 1: bootstrap form input select

<div class="col-lg-6 col-md-6 col-12">
  <div class="input-group mb-3">
    <div class="input-group-prepend">
      <select class="form-control select2bs4" name="country_code" id="country_code" style="width: 100%">
        <option value="+91">+91</option>
        <option value="+351">+351</option>
        <option value="+1">+1</option>
      </select>
    </div>
    	<input type="text" name="user" class="form-control" placeholder="Email Or Mobile Number">
    </div>
</div>

Example 2: bootsrap textbox

<form>
  <div class="form-group">
    <label for="exampleFormControlInput1">Email address</label>
    <input type="email" class="form-control" id="exampleFormControlInput1" placeholder="[email protected]">
  </div>
  <div class="form-group">
    <label for="exampleFormControlSelect1">Example select</label>
    <select class="form-control" id="exampleFormControlSelect1">
      <option>1</option>
      <option>2</option>
      <option>3</option>
      <option>4</option>
      <option>5</option>
    </select>
  </div>
  <div class="form-group">
    <label for="exampleFormControlSelect2">Example multiple select</label>
    <select multiple class="form-control" id="exampleFormControlSelect2">
      <option>1</option>
      <option>2</option>
      <option>3</option>
      <option>4</option>
      <option>5</option>
    </select>
  </div>
  <div class="form-group">
    <label for="exampleFormControlTextarea1">Example textarea</label>
    <textarea class="form-control" id="exampleFormControlTextarea1" rows="3"></textarea>
  </div>
</form>