从我的评论来看

使用背景渐变，它不会在边缘上弯曲

null

.box-input {
  width: 100px;
  height: 100px;
  border-radius: 20px;
  background:linear-gradient(to right, #a3befa 9px, transparent 9px);
  box-shadow: -6px -6px 10px rgba(255, 255, 255, 0.8), 6px 6px 10px rgba(0, 0, 0, 0.2);
}

<div class="box-input"></div>

这就是你想要的吗？

null

* {margin:0; padding:0;}
.inner {
  border-left: 10px solid blue;
  background:yellow;
  height:200px;
  width:500px;
  border-radius:25px;
}
.outer {
  border-radius:25px;
}

<div class="outer">
  <div class="inner">
    Some text ...
  </div>
</div>

您还可以使用csspseudo类。在我的解决方案中，我使用了::before

null

.wrapper {
    display: inline-block;
    padding: 10px 10px 10px 30px;
    position: relative;
    border-radius: 25px;
    overflow: hidden;
    max-width: 450px;
    font-style: italic;
    box-shadow: 0 0 20px -12px;
}

.wrapper::before {
    content: '';
    width: 10px;
    background: #8ac1e8;
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
}
p.message {
    margin-top: 0;
    font-size: 25px;
}
.bottom_info_wrap {
    display: flex;
    justify-content: space-between;
    padding-right: 10px;
}
span.user_name {
    color: #444444;
}
.bottom_info {
    color: #6d6d6d;
}
span.time {
    margin-left: 10px;
}

<main>
    <div class="wrapper">
        <p class="message"> Make a drink and we'll tell you where you'll meet your soulmate
        </p>
    <div class="bottom_info_wrap">
        <span class="user_name">Carl Johnson</span>
        <div class="bottom_info">
            <span class="date">September 26, 2020 </span>
            <span class="time">1 min</span>
        </div>
     </div>
    </div>
</main>