feat: add graceful shutdown handling to sampling HTTP client example

Add signal handling for SIGINT and SIGTERM to allow graceful shutdown
of the sampling HTTP client example. This prevents indefinite blocking
and provides better production-ready behavior.

Addresses review comment about adding graceful shutdown handling.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: andig

examples/sampling_http_client/main.go

@@ -4,6 +4,9 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"os"
+	"os/signal"
+	"syscall"
 
 	"github.com/mark3labs/mcp-go/client"
 	"github.com/mark3labs/mcp-go/client/transport"
@@ -101,8 +104,13 @@ func main() {
 	// For this example, we'll just demonstrate that it's working
 
 	// Keep the client running (in a real app, you'd have your main application logic here)
+	sigChan := make(chan os.Signal, 1)
+	signal.Notify(sigChan, os.Interrupt, syscall.SIGTERM)
+
 	select {
 	case <-ctx.Done():
 		log.Println("Client context cancelled")
+	case <-sigChan:
+		log.Println("Received shutdown signal")
 	}
 }