I want to process the value obtained by Firebase with Forach.
To processed in order, async, await was used.

```
const sleep = time => new Promise(resolve => setTimeout(resolve, time));
 async function () {
   var snapshot = await firebase.database().ref("/path/").once("value")
   snapshot.forEach(async function (childSnapshot) {
       await sleep(1000)
       console.log(snapshot.val)
   })
 }

```

However, as a result only the first item of the first is processed. 
That is, Foreach is not working.
Foreach will work if you remove async, await.
How can we make them compatible?