Bootstrap min fixed width inside flex

Question

I trying to make a search bar with bootstrap smth similar to holidaypiratescom search field.

I need to have min width on first and last button, while letting the 3 form fields to flex. If i set the width directly with css(min-width) the button element is sticks outside of the card when i shrink the screen. Have no idea how to do it, any suggestions?

<div class="card">
<div class="search-box d-md-inline-flex">

<!-- col1 -->
<div class="card border-0">
  <input class="btn btn-primary" type="text" name="" value="All categories">
</div>
<!-- col2 -->
<div class="card border-0">
    <input class="form-control mr-2" type="text" name="departure" placeholder="Departure">
</div>
<!-- col3 -->
<div class="card border-0">
    <input class="form-control mr-2" type="text" name="destination" placeholder="Destination">
</div>
<!-- col4 -->
<div class="card border-0">
    <input class="form-control mr-2" type="text" name="type" placeholder="Travel Period">
</div>
<!-- Submit -->
<div class="card border-0">
    <input class="btn btn-primary" type="submit" name="" value="go">
</div>

</div><!--/search-box -->
</div> <!-- /card -->

Answer 1

<div class="card container">
    <div class="container">
      <div class="search-box d-md-inline-flex">

      <!-- col1 -->
      <div class="card border-0 p-3">
        <input class="btn btn-primary" type="text" name="" value="All categories">
      </div>
      <!-- col2 -->
      <div class="card border-0 p-3">
          <input class="form-control mr-2" type="text" name="departure" placeholder="Departure">
      </div>
      <!-- col3 -->
      <div class="card border-0 p-3">
          <input class="form-control mr-2" type="text" name="destination" placeholder="Destination">
      </div>
      <!-- col4 -->
      <div class="card border-0 p-3">
          <input class="form-control mr-2" type="text" name="type" placeholder="Travel Period">
      </div>
      <!-- Submit -->
      <div class="card border-0 p-3">
          <input class="btn btn-primary" type="submit" name="" value="go">
      </div>

      </div><!--/search-box -->
    </div>
  </div>

Use the container class to wrap the content. For responsive use lg, md, sm for the classes.