• Do not test for vendor dir existence in post-extract, always vendor. Distfiles served by module proxy do not include vendored deps.

• Flatten ${DISTDIR}/go hierarchy a bit by substituting / with _ in ${PKGORIGIN}
• Vendor dependencies in post-extract. We still need to do this to be able to apply local port patches to dependencies.

• Clean the whole GOPATH on distclean

• Set GOPATH to ${DISTDIR}/go/${PKGORIGIN}
• Hook up cleaning module cache to distclean

In D28184#629947, @adamw wrote:

AFAIK this would be the first instance of distfiles being fetched by anything except fetch(1).

In D28184#629947, @adamw wrote:

This is a clever approach! If I'm reading it correctly, this should also fix the case of unnecessary (i.e. test/bench) modules being dragged in and not used in the final build.

Add GO_GOSUMDB variable.

With this patch applied, the Go test suite passes on both current (818390ce0ca) and stable/12 (49038d1723a). Thanks!