Bootstrap 4: No spaces between columns

so I have this problem with columns in bootstrap 4. I wrote this code but in the browser, there's no space between the 3 blocks. Each block has 4 columns but no margin between them.

I tried to change the bootstrap 4 lines for padding but it made things worse but however, here is the code attached in codepen. You can have a live view of the results and you can edit it if you want.

You can see it here in this link: https://codepen.io/PlatoCode/pen/erWaXg

<section class="jobs">
 <div class="container">
      <div class="row">
           <div class="col-md-4 single_job">
                <span style="color: rgb(232, 61, 98);">toronto, canada</span>
                <h5>Web Designer</h5>
                <p>Development Team</p>
                <a href="#" class="btn" style="background-color: rgb(232,61,98);">Apply Now</a>
           </div>
           <div class="col-md-4 single_job">
                <span style="color: rgb(232, 61, 98);">toronto, canada</span>
                <h5>Web Designer</h5>
                <p>Development Team</p>
                <a href="#" class="btn" style="background-color: rgb(232,61,98);">Apply Now</a>
           </div>
           <div class="col-md-4 single_job">
                <span style="color: rgb(232, 61, 98);">toronto, canada</span>
                <h5>Web Designer</h5>
                <p>Development Team</p>
                <a href="#" class="btn" style="background-color: rgb(232,61,98);">Apply Now</a>
           </div>
      </div>
 </div>

CSS :-

 /*----- General ----*/
 html { -webkit-font-smoothing: antialiased;
  }
 body {
    font-family: "Open Sans", sans-serif;
    font-weight: 400;
    color: #1c1c1c;
    height: 100%;
    min-height: 100%;
 }

 h1, h2, h3, h4, h5, h6 {
    font-family: 'Montserrat', sans-serif;
    line-height: 1;
    color: #1c1c1c;
    margin-top: 0
 }

 h1 {
    font-size: 2.813em;
 }

 h2 {
    font-size: 2.5em;
 }

 h3 {
    font-size: 2em;
 }

 h4 {
    font-size:  1.438em;
 }

 h5 {
    font-size: 1.25em;
 }

 h6 {
    font-size: 1.125em;
 }

 ul,
 ol {
   list-style: none;
   line-height: 1.85714286em;
 }

 p {
    font-family: 'Roboto';
    font-size: 0.938em;
    color: #889094;
 }

 .btn {
    display: inline-block;
    background-color: #50b1fc;
    text-align: center;
    cursor: pointer;
    color: #fff;
    border-radius: 38px;
    font-family: 'Montserrat', sans-serif;
    font-size: 11px;
    letter-spacing: 1px;
    text-transform: uppercase;
    overflow: hidden;
    position: relative;
    z-index: 0;
    vertical-align: middle;
    -moz-user-select: none;
    -webkit-user-select: none;
    user-select: none;
    text-decoration: none;
    text-shadow: none;
    padding: 10px 30px;
 }

 .btn:hover {
    color: white;
 }

 .btn2 {
    display: inline-block;
    background-color: #fff;
    text-align: center;
    cursor: pointer;
    color: #010d2f;
    border-radius: 10px;
    font-family: 'Montserrat', sans-serif;
    font-size: 11px;
    letter-spacing: 1px;
    text-transform: uppercase;
    overflow: hidden;
    position: relative;
    z-index: 0;
    vertical-align: middle;
    -moz-user-select: none;
    -webkit-user-select: none;
    user-select: none;
    text-decoration: none;
    text-shadow: none;
    padding: 10px 30px;
 }

 .btn2:hover {
    color: #010d2f;
 }


 /* Jobs */

 .single_job {
    background-color: #fff;
    -webkit-box-shadow: 0 0 38px rgba(0,0,0,.08);
    -moz-box-shadow: 0 0 38px rgba(0,0,0,.08);
    box-shadow: 0 0 38px rgba(0,0,0,.08);
    padding: 35px 25px;
 }

 .single_job p {
    margin-bottom: 25px;
 }
 .single_job h5 {
    margin-top: 5px;
 }