chore(go): add text-to-speech samples (#3253)

Author: hugoaguirre

go/samples/text-to-speech/genkit.wav

@@ -0,0 +1,95 @@
+// 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 main
+
+import (
+	"context"
+	"encoding/base64"
+	"io"
+	"log"
+	"os"
+
+	"github.com/firebase/genkit/go/ai"
+	"github.com/firebase/genkit/go/genkit"
+	"github.com/firebase/genkit/go/plugins/googlegenai"
+	"google.golang.org/genai"
+)
+
+func main() {
+	ctx := context.Background()
+
+	// Initialize Genkit with the Google AI plugin. When you pass nil for the
+	// Config parameter, the Google AI plugin will get the API key from the
+	// GEMINI_API_KEY or GOOGLE_API_KEY environment variable, which is the recommended
+	// practice.
+	g, err := genkit.Init(ctx,
+		genkit.WithPlugins(&googlegenai.GoogleAI{}),
+		genkit.WithDefaultModel("googleai/gemini-2.5-flash-preview-tts"),
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Define a simple flow that generates an audio from a given text
+	genkit.DefineFlow(g, "text-to-speech-flow", func(ctx context.Context, input any) (string, error) {
+		resp, err := genkit.Generate(ctx, g,
+			ai.WithConfig(&genai.GenerateContentConfig{
+				Temperature:        genai.Ptr[float32](1.0),
+				ResponseModalities: []string{"AUDIO"},
+				SpeechConfig: &genai.SpeechConfig{
+					VoiceConfig: &genai.VoiceConfig{
+						PrebuiltVoiceConfig: &genai.PrebuiltVoiceConfig{
+							VoiceName: "Algenib",
+						},
+					},
+				},
+			}),
+			ai.WithPrompt("Say: Genkit is the best Gen AI library!"))
+		if err != nil {
+			return "", err
+		}
+
+		// base64 encoded audio
+		text := resp.Text()
+		return text, nil
+	})
+
+	// Define a simple flow that generates audio transcripts from a given audio
+	genkit.DefineFlow(g, "speech-to-text-flow", func(ctx context.Context, input any) (string, error) {
+		audio, err := os.Open("./genkit.wav")
+		if err != nil {
+			return "", err
+		}
+		defer audio.Close()
+
+		audioBytes, err := io.ReadAll(audio)
+		if err != nil {
+			return "", err
+		}
+		resp, err := genkit.Generate(ctx, g,
+			ai.WithModelName("googleai/gemini-2.5-flash"),
+			ai.WithMessages(ai.NewUserMessage(
+				ai.NewTextPart("Can you transcribe the next audio?"),
+				ai.NewMediaPart("audio/wav", "data:audio/wav;base64,"+base64.StdEncoding.EncodeToString(audioBytes)))),
+		)
+		if err != nil {
+			return "", err
+		}
+
+		return resp.Text(), nil
+	})
+
+	<-ctx.Done()
+}