all: add go.mod

Commands run:
	go mod init
	go mod edit -go=1.11
	go mod tidy
	go list -m all
	go test ./...

Updates golang/go#30228

Change-Id: I43900a3d2b59ddb7701436a652ac00e35a49c69d
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/167177
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..cba8457
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module golang.org/x/benchmarks
+
+go 1.11
+
+require golang.org/x/sys v0.0.0-20190312061237-fead79001313
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..cf6edbd
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+golang.org/x/sys v0.0.0-20190312061237-fead79001313 h1:pczuHS43Cp2ktBEEmLwScxgjWsBSzdaQiKzUyf3DTTc=
+golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=