weiznich/diesel_async

AI Summary: The task is to debug and fix a compilation error in the `diesel-async` crate related to lifetime issues when using pipelining with `try_join` on futures returned by Diesel queries. The error stems from mismatched types and insufficiently general `FnOnce` implementations, likely due to the complexities of GATs (Generalized Associated Types) and lifetime management in asynchronous contexts. The solution involves either explicitly erasing lifetimes or refining the type signatures within `diesel-async` to correctly handle the lifetimes of the futures.