我在写一个测试案例。在清理期间，测试用例应该
1.删除所有收藏
1.确认已删除集合
1.重新创建收藏
据我所知，createCollection和dropCollection返回Promises-https：//mongoosejs.com/docs/api/connection.html#Connection.prototype.dropCollection（）
我想等待Promises按顺序完成。我想我会使用await，但我不能嵌入await s。我如何重写代码？

const collectionsBeforeDrop = await db.collections();
collectionsBeforeDrop.forEach(c => {
      console.log(`got collection name : ${c.collectionName}`);
      await db.dropCollection(c); <-- can't use await here
    });
    console.log(`checking after cleanup`)
    const collectionsAfterDrop = await db.collections();
    collectionsAfterDrop.forEach(c => {
      console.log(`got collection name after claanup! THIS SHOULDN'T HAVE HAPPENED : ${c.collectionName}`);
      throw new Error("couldn't clean up after test case");
    });

console.log(`creating collections again`);
collectionsBeforeDrop.forEach(c => {
  console.log(`got collection name : ${c.collectionName}`);
  await db.createCollection(c) <-- can't use await unless at top level
  .then(()=>{
    console.log(`checking after recreating collections`)
    await db.collections() <-- can't use await unless at top level
    .then((collectionsAfterRecreation)=>{
      collectionsAfterRecreation.forEach(c => {
        console.log(`got collection name after claanup! THIS SHOULDN'T HAVE HAPPENED : ${c.collectionName}`);
      });
    })
  })
});