gradient border with border radius

demo.md

<div class="container">
<a  class="button" href="#"><span>Login</span></a>
</div>

.button {
  background: linear-gradient(to right, #05FBFF,#1E00FF);
  border-radius: 8px;
  color: #122dff;
  display: inline-block;
  font-size: 20px;
  padding: 1px;
  text-decoration: none;
}
.button span {
  background: #fff;
  display: block;
  padding: 1em 3em;
  border-radius: 6px;
}


.container {
  text-align: center;
  margin-top: 30px;
}