go help modules (and equivalently https://golang.org/cmd/go/#hdr-Modules__module_versions__and_more) is the original reference page for modules. It's fairly long for an introduction, but at the same time, it doesn't go into enough detail or provide enough examples to be a thorough reference.

https://golang.org/ref/mod is intended to replace go help modules as a detailed reference. In Go 1.16, we should change go help modules to point to that.

A few other help pages have this problem, in particular, go help module-get (https://golang.org/cmd/go/#hdr-Add_dependencies_to_current_module_and_install_them). The help page for each command should provide a brief synopsis of its arguments and flags, then should point to reference documentation like https://golang.org/ref/mod#go-get for more detail.

Related #33637.