Bump plugin client version (#1319)

* Bump plugin client version

Signed-off-by: Carlisia <carlisiac@vmware.com>

pkg/plugin/framework/handshake.go

@@ -0,0 +1,32 @@
+/*
+Copyright 2019 the Velero contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package framework
+
+import plugin "github.com/hashicorp/go-plugin"
+
+// Handshake returns the configuration information that allows go-plugin clients and servers to perform a handshake.
+func Handshake() plugin.HandshakeConfig {
+	return plugin.HandshakeConfig{
+		// The ProtocolVersion is the version that must match between Velero framework
+		// and Velero client plugins. This should be bumped whenever a change happens in
+		// one or the other that makes it so that they can't safely communicate.
+		ProtocolVersion: 2,
+
+		MagicCookieKey:   "VELERO_PLUGIN",
+		MagicCookieValue: "hello",
+	}
+}