all: add go.mod

Commands run:
	sed -i 's;// +build OMIT;// +build ignore,OMIT;' $(grep -l OMIT -r)
	go mod init
	go mod edit -go=1.11
	go mod tidy
	go list -m all
	go test ./...

Updates golang/go#30228
Updates golang/go#29598

Change-Id: I3d0a4787c1158572bed8dd3785ff02e16d1cc1f3
Reviewed-on: https://go-review.googlesource.com/c/talks/+/167159
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
362 files changed