How can I use async/await in the Vue 3.0 setup() function using Typescript

Try to use onMounted hook to manipulate asynchronous call :

 setup() {
    const users = ref([]);
    onMounted(async () => {
      const res = await axios.get("https://jsonplaceholder.typicode.com/users");
      users.value = res.data;
      console.log(res);
    });

    return {
      users,
    };
  },

LIVE DEMO

According to official docs the Best approach is to use async setup in child component and wrap that component by Suspense component in the parent one :

UserList.vue

<script  lang="ts">
import { defineComponent } from "vue";
export default defineComponent({
    async setup() {
        //get users from jsonplacerholder using await fetch api 
        const users = await fetch("https://jsonplaceholder.typicode.com/users").then(res => res.json());

        return {
            users
        }
    }
})
</script>
<template>
    <div>
        <!-- list users -->
        <ul>
            <li v-for="user in users">{{ user.name }}</li>
        </ul>
    </div>
</template>

Parent component:

<script lang="ts">

import UserList from "../components/tmp/UserList.vue";
...
</script>

   <div>
            <!-- Suspense component  to show users  -->
            <Suspense>
                <template #fallback>
                    <div>loading</div>
                </template>

                <UserList />
            </Suspense>
        </div>