All promises in async functions must be used

When using async / await, it can be easy to forget to await a promise which can result in async tasks running in an unexpected order. Thus, we require that every promise in an async function is consumed in some way, so that there's a well-defined order in which async tasks are resolved. To fix this check, you can do one of the following:

1. Remove async from the function, and instead use normal promise chaining.
2. await the promise.
3. Assign the promise to a variable and await it later.

As a last resort, if you really want to use async and can't await the promise, you can just assign it to a variable, like so

let ignoredPromise = returnsPromise();

This makes your intent to ignore the result of the promise explicit, although it may cause “declared but never used” warning with some linters.