; 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:

        edit        edit go.mod from tools or scripts
        fix         make go.mod semantically consistent
        graph       print module requirement graph
        init        initialize new module in current directory
        tidy        add missing and remove unused modules
        vendor      make vendored copy of dependencies
        verify      verify dependencies have expected content

Use "go help mod <command>" for more information about a command.

panic: runtime error: index out of range

goroutine 1 [running]:
main.main()
        /g/src/github.com/golang/go/src/cmd/go/main.go:197 +0x1a28