Add pluggable transport interface + WebSocket support

simplify API by using interface{}, rename from transport -> stream

add WebSocket transport in websocket subpackage

do not buffer in ReadObject, rename GetObjectReader/ReadObject -> NextObjectReader

use xtest (jsonrpc2_test) package to allow us to test subpackages that depend on us (in a future change)

factor out vscode-specific transport code and allow pluggable transports

remove Server (unused) and Serve (unnecessary):
  The Serve func had nothing specific to JSON-RPC; it was just a loop
  around (net.Listener).Accept. It added no value.

websocket/stream.go

@@ -0,0 +1,44 @@
+// Package websocket provides WebSocket transport support for JSON-RPC
+// 2.0.
+package websocket
+
+import (
+	"io"
+
+	"github.com/gorilla/websocket"
+)
+
+// A ObjectStream is a jsonrpc2.ObjectStream that uses a WebSocket to
+// send and receive JSON-RPC 2.0 objects.
+type ObjectStream struct {
+	conn *websocket.Conn
+}
+
+// NewObjectStream creates a new jsonrpc2.ObjectStream for sending and
+// receiving JSON-RPC 2.0 objects over a WebSocket.
+func NewObjectStream(conn *websocket.Conn) ObjectStream {
+	return ObjectStream{conn: conn}
+}
+
+// WriteObject implements jsonrpc2.ObjectStream.
+func (t ObjectStream) WriteObject(obj interface{}) error {
+	return t.conn.WriteJSON(obj)
+}
+
+// ReadObject implements jsonrpc2.ObjectStream.
+func (t ObjectStream) ReadObject(v interface{}) error {
+	err := t.conn.ReadJSON(v)
+	if e, ok := err.(*websocket.CloseError); ok {
+		if e.Code == websocket.CloseAbnormalClosure && e.Text == io.ErrUnexpectedEOF.Error() {
+			// Suppress a noisy (but harmless) log message by
+			// unwrapping this error.
+			err = io.ErrUnexpectedEOF
+		}
+	}
+	return err
+}
+
+// Close implements jsonrpc2.ObjectStream.
+func (t ObjectStream) Close() error {
+	return t.conn.Close()
+}