Since we are now building on Go 1.11 (as of 074a2d4f (all: use Go 1.11
in CI, 2018-08-28)) and Go 1.11 supports Go Modules [1], let's stop
using Glide, and begin using Go Modules.
This involves a few things:
* Teach the Makefile how to build go.sum files instead of glide.lock
files.
* Teach continuous integration services to build Git LFS in a
non-$GOPATH environment, since (without setting GO111MODULE=on
explicitly, which we choose not to do), this will break compiling
Git LFS, because Go 1.11 will ignore modules present in a Go
checkout beneath $GOPATH.
* In order to do the above, let's also make sure that we are
un-setting $GOCACHE in the environment, as this causes Go to work
without modules support [2].
* Because we're no longer building in a `$GOPATH`-based location,
let's instruct the CircleCI base image to archive the new location,
too.
* Similarly, teach the RPM spec to build in a non-$GOPATH location.
* By contrast, since we use dh_golang to build git-lfs binaries on
Debian, let's wait until the upstream dh_golang package is released
with support for Go 1.11 module support explicitly. Therefore, force
GO111MODULE to be on so that we can build a copy of Git LFS whose
checkout is within a $GOPATH.
Although the go.mod versions match the glide.yaml ones, the diff
attached is large because Go Modules do not vendor `_test.go` files,
whereas Glide does.
[1]: https://golang.org/doc/go1.11#modules
[2]: `GOCACHE=on` will be deprecated in Go 1.12, so this change makes
sense for that reason, too.
Co-authored-by: brian m. carlson <bk2204@github.com>