async_trait -> async functions in traits

[Twister915]

Is it possible to allow users to avoid boxed futures by using the async fn in traits feature?

First such trait I ran into which this would apply to is called QueryParser (pgwire::api::stmt::QueryParser), but there are many in this crate.

[sunng87]

hello @Twister915 , I didn't follow the status of async function in trait these days, could you provide me a pull request as a sample? And if it's conflict with current async_trait method, we can use the feature gate to control that switch if possible.