module commands like 'go get' and 'go mod vendor' from a directory
in GOROOT/src.

Maintaining vendor directories
==============================

Before updating vendor directories, ensure that module mode is enabled.
Make sure that GO111MODULE is not set in the environment, or that it is
set to 'on' or 'auto', and if you use a go.work file, set GOWORK=off.

Requirements may be added, updated, and removed with 'go get'.