練習題 2

https://www.kablamo.com.au/blog-1/2018/12/10/just-tell-me-how-to-use-go-modules?fbclid=IwAR1-oK9GV6xShtN01GcPndJ2WT-ltBDSdk7RC7XTNrbrI1wYMeL2MHJBJVU

1. GO111MODULES

$ export GO111MODULES=on

2. init

$ go mod init github.com/JasonYCHuang/todo

3. update

$ go get -u <repo url>

$ go mod vendor