flex auto 设置两端对齐

HTML

<section>
    <div>left1div>
    <div>left2div>
    <div class="right">left3div>
section>

CSS

section {
    display: flex;
}

div {
    width: 100px;
    height: 100px;
    background: antiquewhite;
}

.right {
    margin-left: auto;
}