not able to cargo build 4-routing

[chen116]

Hi,

First of all, thanks you so much for this repo. I am new to rust and having a hard time to get lapin to work along with async and all that fun stuff. Very appreciate your work. Anyway, I was able to build and run all 6 scenarios but not
"4-routing." I guess it can be a good exercise for me to try to fix it, but just want to see if 4-routing compiles normal for you.