bootstrap-overlay-loading.css

.hidden {
  visibility: hidden;
}

.loader-overlay {
  position: fixed;
  width: 100%;
  height: 100vh;
  // z-index: 1000;
  background-color:rgba(0,0,0,0.5);
  top: 0;
  z-index: 1109;
}

.popup-spinner{
  margin-top: 15%;
  top: 0;
  // position: absolute;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1110;
}

.loader {
  height: 4px;
  width: 100%;
  position: relative;
  overflow: hidden;
  background-color: #FFF;
}

.loader:before {
  display: block;
  position: absolute;
  content: "";
  left: -200px;
  width: 200px;
  height: 4px;
  background-color: orange;
  animation: loading 2s linear infinite;
}

@keyframes loading {
  from {
    left: -200px;
    width: 30%;
  }

  50% {
    width: 30%;
  }

  70% {
    width: 70%;
  }

  80% {
    left: 50%;
  }

  95% {
    left: 120%;
  }

  to {
    left: 100%;
  }
}

bootstrap-overlay-loading.html

    <div class="loader-overlay">
      <div class="popup-spinner">
        <div class="card" style="width: 18rem;">
          <div class="card-body">
            <div class="text-center">
              <h4>Aguarde</h4>
              <br>
            </div>
            <div class="progress">
              <div class="progress-bar progress-bar-striped progress-bar-animated" role="progressbar" aria-valuenow="100"
                aria-valuemin="0" aria-valuemax="100" style="width: 100%"></div>
            </div>
          </div>
        </div>
      </div>
    </div>