feat(genai): Add samples for vertexAI express mode api key

genai/express_mode/expressmode_with_api_key.go

@@ -0,0 +1,64 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package express_mode shows how to use the GenAI SDK to generate text with VertexAI Api Key.
+package express_mode
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"google.golang.org/genai"
+)
+
+var newClient = genai.NewClient
+
+// generateContent shows how to use Vertex AI Express mode with an API key.
+func generateContentWithApiKey(w io.Writer) error {
+	ctx := context.Background()
+
+	// TODO(developer): Replace with your actual API key
+	apiKey := "YOUR_API_KEY"
+
+	client, err := newClient(ctx, &genai.ClientConfig{
+		APIKey:      apiKey,
+		HTTPOptions: genai.HTTPOptions{APIVersion: "v1"},
+	})
+	if err != nil {
+		return fmt.Errorf("failed to create genai client: %w", err)
+	}
+
+	modelName := "gemini-2.5-flash"
+	resp, err := client.Models.GenerateContent(ctx, modelName,
+		[]*genai.Content{
+			{Parts: []*genai.Part{
+				{Text: "Explain bubble sort to me."},
+			}, Role: "user"},
+		},
+		nil,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to generate content: %w", err)
+	}
+
+	fmt.Fprintln(w, resp.Text())
+
+	// Example response:
+	// Bubble Sort is a simple sorting algorithm that repeatedly steps through the list
+
+	return nil
+}
+
+// [END googlegenaisdk_vertexai_express_mode]

genai/express_mode/expressmode_with_api_key_test.go

@@ -0,0 +1,47 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package express_mode
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	"github.com/GoogleCloudPlatform/golang-samples/internal/testutil"
+)
+
+func TestExpressModeGenerationIntegration(t *testing.T) {
+	tc := testutil.SystemTest(t)
+
+	t.Setenv("GOOGLE_GENAI_USE_VERTEXAI", "1")
+	t.Setenv("GOOGLE_CLOUD_LOCATION", "us-central1")
+	t.Setenv("GOOGLE_CLOUD_PROJECT", tc.ProjectID)
+
+	apiKey := os.Getenv("YOUR_API_KEY")
+	if apiKey == "" {
+		t.Skip("skipping integration test: GOOGLE_API_KEY not set")
+	}
+
+	buf := new(bytes.Buffer)
+	err := generateContentWithApiKey(buf)
+	if err != nil {
+		t.Fatalf("generateContentWithApiKey failed: %v", err)
+	}
+
+	output := buf.String()
+	if output == "" {
+		t.Error("expected non-empty output, got empty")
+	}
+}