Go: stop RPC client logging expected errors (#609)

* Go: RPC client loop expects stdout close

* handle body read errors similarly

Author: chlowell

go/internal/jsonrpc2/jsonrpc2.go

@@ -4,8 +4,10 @@ import (
 	"bufio"
 	"crypto/rand"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
+	"os"
 	"reflect"
 	"sync"
 	"sync/atomic"
@@ -320,7 +322,7 @@ func (c *Client) readLoop() {
 			line, err := reader.ReadString('\n')
 			if err != nil {
 				// Only log unexpected errors (not EOF or closed pipe during shutdown)
-				if err != io.EOF && c.running.Load() {
+				if err != io.EOF && !errors.Is(err, os.ErrClosed) && c.running.Load() {
 					fmt.Printf("Error reading header: %v\n", err)
 				}
 				return
@@ -345,7 +347,10 @@ func (c *Client) readLoop() {
 		// Read message body
 		body := make([]byte, contentLength)
 		if _, err := io.ReadFull(reader, body); err != nil {
-			fmt.Printf("Error reading body: %v\n", err)
+			// Only log unexpected errors (not EOF or closed pipe during shutdown)
+			if err != io.EOF && !errors.Is(err, os.ErrClosed) && c.running.Load() {
+				fmt.Printf("Error reading body: %v\n", err)
+			}
 			return
 		}