Add support for go-modules

[alok87]

Add support for go-modules

[tallclair]

Can you elaborate on what's needed here? I thought go-modules were still vendored into .../vendor? Or did you mean export a go-module for godepq?

[liggitt]

I think it was describing dependencies at the module level

• module A depends on [B,C,D]
• module W is depended on by [X,Y,Z]

go mod graph includes much of this info in raw form, but doesn't let you see the full transitive list of dependencies