ci: add test for websocket

vendor/github.com/gorilla/websocket/examples/command/README.md

@@ -0,0 +1,19 @@
+# Command example
+
+This example connects a websocket connection to stdin and stdout of a command.
+Received messages are written to stdin followed by a `\n`. Each line read from
+standard out is sent as a message to the client.
+
+    $ go get github.com/gorilla/websocket
+    $ cd `go list -f '{{.Dir}}' github.com/gorilla/websocket/examples/command`
+    $ go run main.go <command and arguments to run>
+    # Open http://localhost:8080/ .
+
+Try the following commands.
+
+    # Echo sent messages to the output area.
+    $ go run main.go cat
+
+    # Run a shell.Try sending "ls" and "cat main.go".
+    $ go run main.go sh
+