blake2s: register BLAKE2s

Register BLAKE2s-256 if the package is imported.
Change-Id: Ib415ae641f21d863720bf9c089017ee97654a555
Reviewed-on: https://go-review.googlesource.com/36878
Reviewed-by: Matt Layher <mdlayher@gmail.com>
Reviewed-by: Adam Langley <agl@golang.org>
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

blake2s/register.go

@@ -0,0 +1,21 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.9
+
+package blake2s
+
+import (
+	"crypto"
+	"hash"
+)
+
+func init() {
+	newHash256 := func() hash.Hash {
+		h, _ := New256(nil)
+		return h
+	}
+
+	crypto.RegisterHash(crypto.BLAKE2s_256, newHash256)
+}