Reconsider futures-based interface

[theduke]

I really need to have a asynchronous interface to Arango.

reqwest already provides the reqwest::r#async::Client async client that can be used easily. It would need an additional refactor and major version bump when async/await hits stable, but that will only happen in late September.

Let me know if you'll accept a PR, otherwise I'll just roll my own.

[fMeow]

Yes, arangors is open to PR on async client, which are on the next milestone. So feel free to submit PR. We can have more disscussion on how to embed async support into arangors.

I prefer to use a generic client as a warpper for both async and sync client. And refactor all related operation with Trait to keep a consistent API between sync and async.

I am waiting for the async/await syntax in stable channel. I would like to stick to futures 0.3 ecosystem. So reqwest may not be a good choice if we want a fully async/await arango client for rust. But I'm not sure.

[thedodd]

@guoli-lyu looks like some interesting progress is being made on this front seanmonstar/reqwest#565

[fMeow]

Reqwest is making progress toward aysnc/await. I don't want arangors to be a nightly only crate, so I will starts working on this in another branch.

[fMeow]

Finally arangors supports async syntax in 0.3.0.

In 0.3.0, you can toggle between async or sync with correct feature gate. Also, you can choose any HTTP client backend.

[inzanez]

@fMeow very nice, many thanks! I really appreciate the switch to 'thiserror' too!