➜ ~ go mod
Go mod provides access to operations on modules. 
Note that support for modules is built into all the go commands, not just 'go mod'. For example, day-to-day adding, removing, upgrading, and downgrading of dependencies should be done using 'go get'. 
See 'go help modules' for an overview of module functionality. 
Usage: go mod <command> [arguments] 
The commands are: 
download download modules to local cache 下载依赖的 module 到本地 cache 
edit edit go.mod from tools or scripts 编辑 go.mod graph print module requirement graph 打印模块依赖图 
init initialize new module in current directory 在当前目录下初始化 go.mod(就是会新建一个 go.mod 文件) 
tidy add missing and remove unused modules 整理依赖关系，会添加丢失的 module，删除不需要的 module 
vendor make vendored copy of dependencies 将依赖复制到 vendor 下 
verify verify dependencies have expected content 校验依赖 why explain why packages or modules are needed 解释为什么需要依赖 Use "
go help mod <command>"
 for more information about a command.