How tokio join macro works

tokio's join macro is pretty amazing

https://docs.rs/tokio/0.2.20/tokio/macro.join.html

To find out how this join! macro works exactly,  you can do blow to expand the macro to see exact code generated.

rustup toolchain install nightly
cargo install cargo-expand

then in your project

cargo expand

You will find the expanded code like below

Usage of serde_json

Some sample code shows behavior of serde_json.

I used to write code like

val.as_object().unwrap().get("field_name").unwrap().as_object().unwrap().get_("sub_field_name").as_str().unwrap().

Turns out that using index of serde_json makes code much less verbose.