my own answer about rustlings, reference only😊
the exercise v0.1 folder update to 20200623,
the exercise v0.2 folder update to 20200913,
the exercise V0.3 folder update to 20210204,
the exercise V0.4 folder update to 20210804, <----The lastest version consistent with origin repo
I will update as long as the original repo update🦀