chore(example): context propagation and signal-based cancellation (google#237)

* refactor(mcp): integrate context propagation and signal-based cancellation

- Add signal handling to gracefully cancel the context on interrupt (SIGINT, SIGTERM)
- Update functions to accept context instead of creating a new one internally
- Pass the main context to MCP transport constructors for improved cancellation support

Signed-off-by: appleboy <appleboy.tw@gmail.com>

* refactor: improve signal handling and cleanup unused imports

- Remove unused import of syscall
- Create cancellation context only for SIGINT (Ctrl+C), not SIGTERM

Signed-off-by: appleboy <appleboy.tw@gmail.com>

* style: adopt Go-style octal file permissions throughout codebase

- Use Go-style octal notation (0o) for file permission arguments in os.MkdirAll and os.WriteFile
- Remove a few unnecessary blank lines at the end of main functions

Signed-off-by: appleboy <appleboy.tw@gmail.com>

---------

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Author: appleboy

examples/mcp/main.go

@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"os/signal"
 	"strings"
 
 	"github.com/modelcontextprotocol/go-sdk/mcp"
@@ -58,32 +59,34 @@ func GetWeather(ctx context.Context, req *mcp.CallToolRequest, input Input) (*mc
 	}, nil
 }
 
-func localMCPTransport() mcp.Transport {
+func localMCPTransport(ctx context.Context) mcp.Transport {
 	clientTransport, serverTransport := mcp.NewInMemoryTransports()
 
 	// Run in-memory MCP server.
 	server := mcp.NewServer(&mcp.Implementation{Name: "weather_server", Version: "v1.0.0"}, nil)
 	mcp.AddTool(server, &mcp.Tool{Name: "get_weather", Description: "returns weather in the given city"}, GetWeather)
-	_, err := server.Connect(context.Background(), serverTransport, nil)
+	_, err := server.Connect(ctx, serverTransport, nil)
 	if err != nil {
 		log.Fatal(err)
 	}
 
 	return clientTransport
 }
 
-func githubMCPTransport() mcp.Transport {
+func githubMCPTransport(ctx context.Context) mcp.Transport {
 	ts := oauth2.StaticTokenSource(
 		&oauth2.Token{AccessToken: os.Getenv("GITHUB_PAT")},
 	)
 	return &mcp.StreamableClientTransport{
 		Endpoint:   "https://api.githubcopilot.com/mcp/",
-		HTTPClient: oauth2.NewClient(context.Background(), ts),
+		HTTPClient: oauth2.NewClient(ctx, ts),
 	}
 }
 
 func main() {
-	ctx := context.Background()
+	// Create context that cancels on interrupt signal (Ctrl+C)
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
+	defer stop()
 
 	model, err := gemini.NewModel(ctx, "gemini-2.5-flash", &genai.ClientConfig{
 		APIKey: os.Getenv("GOOGLE_API_KEY"),
@@ -94,9 +97,9 @@ func main() {
 
 	var transport mcp.Transport
 	if strings.ToLower(os.Getenv("AGENT_MODE")) == "github" {
-		transport = githubMCPTransport()
+		transport = githubMCPTransport(ctx)
 	} else {
-		transport = localMCPTransport()
+		transport = localMCPTransport(ctx)
 	}
 
 	mcpToolSet, err := mcptoolset.New(mcptoolset.Config{
@@ -128,5 +131,4 @@ func main() {
 	if err != nil {
 		log.Fatalf("run failed: %v\n\n%s", err, l.CommandLineSyntax())
 	}
-
 }

examples/vertexai/imagegenerator/main.go

@@ -159,13 +159,13 @@ func saveImage(ctx tool.Context, input saveImageInput) saveImageResult {
 
 	// Create an "output" directory in the current working directory if it doesn't exist.
 	outputDir := "output"
-	if err := os.MkdirAll(outputDir, 0755); err != nil {
+	if err := os.MkdirAll(outputDir, 0o755); err != nil {
 		log.Printf("Failed to create output directory '%s': %v", outputDir, err)
 		return saveImageResult{Status: "fail"}
 	}
 
 	localPath := filepath.Join(outputDir, localFilename)
-	err = os.WriteFile(localPath, resp.Part.InlineData.Data, 0644)
+	err = os.WriteFile(localPath, resp.Part.InlineData.Data, 0o644)
 	if err != nil {
 		log.Printf("Failed to write image to local file '%s': %v", localPath, err)
 		return saveImageResult{Status: "fail"}

examples/workflowagents/sequential/main.go

@@ -92,5 +92,4 @@ func main() {
 	if err != nil {
 		log.Fatalf("run failed: %v\n\n%s", err, l.CommandLineSyntax())
 	}
-
 }

examples/workflowagents/sequentialCode/main.go

@@ -30,7 +30,6 @@ import (
 )
 
 func main() {
-
 	ctx := context.Background()
 
 	model, err := gemini.NewModel(ctx, "gemini-2.5-flash", &genai.ClientConfig{})
@@ -148,5 +147,4 @@ Do not add any other text before or after the code block.`,
 	if err != nil {
 		log.Fatalf("run failed: %v\n\n%s", err, l.CommandLineSyntax())
 	}
-
 }