效果如图：
代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style type="text/css">
.div-wrap {
400px;
height: 200px;
background: rgba(220, 223, 230, 0.2);
position: relative;
}
.div-wrap::after {
position: absolute;
content: "";
left: 0;
bottom: 0;
100%;
height: 2px;
background: linear-gradient(90deg,rgba(255, 255, 255, 1) 0%, #08E8FF 50%, rgba(255, 255, 255, 1) 100%);
}
</style>
</head>
<body>
<div class="div-wrap"></div>
</body>
</html>