mcp: fix flaky ExampleLoggingTransport (#483)

Reads are technically racy with writes. Sort for stability.

Author: findleyr

docs/troubleshooting.md

@@ -39,12 +39,15 @@ func ExampleLoggingTransport() {
 	if _, err := client.Connect(ctx, logTransport, nil); err != nil {
 		log.Fatal(err)
 	}
-	fmt.Println(b.String())
+	// Sort for stability: reads are concurrent to writes.
+	for _, line := range slices.Sorted(strings.SplitSeq(b.String(), "\n")) {
+		fmt.Println(line)
+	}
+
 	// Output:
-	// write: {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"capabilities":{"roots":{"listChanged":true}},"clientInfo":{"name":"client","version":"v0.0.1"},"protocolVersion":"2025-06-18"}}
 	// read: {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-06-18","serverInfo":{"name":"server","version":"v0.0.1"}}}
+	// write: {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"capabilities":{"roots":{"listChanged":true}},"clientInfo":{"name":"client","version":"v0.0.1"},"protocolVersion":"2025-06-18"}}
 	// write: {"jsonrpc":"2.0","method":"notifications/initialized","params":{}}
-
 }
 ```
 

mcp/transport_example_test.go

@@ -2,13 +2,18 @@
 // Use of this source code is governed by an MIT-style
 // license that can be found in the LICENSE file.
 
+// Uses strings.SplitSeq.
+//go:build go1.24
+
 package mcp_test
 
 import (
 	"bytes"
 	"context"
 	"fmt"
 	"log"
+	"slices"
+	"strings"
 
 	"github.com/modelcontextprotocol/go-sdk/mcp"
 )
@@ -29,12 +34,15 @@ func ExampleLoggingTransport() {
 	if _, err := client.Connect(ctx, logTransport, nil); err != nil {
 		log.Fatal(err)
 	}
-	fmt.Println(b.String())
+	// Sort for stability: reads are concurrent to writes.
+	for _, line := range slices.Sorted(strings.SplitSeq(b.String(), "\n")) {
+		fmt.Println(line)
+	}
+
 	// Output:
-	// write: {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"capabilities":{"roots":{"listChanged":true}},"clientInfo":{"name":"client","version":"v0.0.1"},"protocolVersion":"2025-06-18"}}
 	// read: {"jsonrpc":"2.0","id":1,"result":{"capabilities":{"logging":{}},"protocolVersion":"2025-06-18","serverInfo":{"name":"server","version":"v0.0.1"}}}
+	// write: {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"capabilities":{"roots":{"listChanged":true}},"clientInfo":{"name":"client","version":"v0.0.1"},"protocolVersion":"2025-06-18"}}
 	// write: {"jsonrpc":"2.0","method":"notifications/initialized","params":{}}
-
 }
 
 // !-loggingtransport