`example/echo.rs` doesn't work concurrently

[giraffate]

Bug Report

https://github.com/tokio-rs/tracing/blob/a8cc977e01ec4e1dce4137e37cfc1bfba7ebbed8/examples/examples/echo.rs doesn't work concurrently. It seems that the commit a8cc977 changed the behavior.

[davidbarsky]

I'm able to reproduce this issue with two instances of netcat. It seems like adding this .await? caused the echo example to no longer be concurrent.