CredentialsProvider credentialsProvider = FixedCredentialsProvider.create(ServiceAccountCredentials.fromStream(new FileInputStream("/path/to/service-account.json")));

ChannelProvider channelProvider = SpeechSettings.defaultChannelProviderBuilder().setCredentialsProvider(credentialsProvider).build();

SpeechSettings settings = SpeechSettings.defaultBuilder().setChannelProvider(channelProvider).build();

// Instantiates a client
SpeechClient speech = SpeechClient.create(settings);

var base64 = Convert.ToBase64String(File.ReadAllBytes(file));

                dynamic request = new
                {
                    config = new
                    {
                        encoding = "LINEAR16",
                        sampleRateHertz = 8000,
                        languageCode = "en-US",
                        enableWordTimeOffsets = false
                    },
                    audio = new
                    {
                        content = base64
                    }
                };

    var json = JsonConvert.SerializeObject(request);
    var requestJson = StringContent(json, Encoding.UTF8, "application/json");

                var client = new HttpClient();

                var speechToText = "";
                var response = await client.PostAsync($"https://speech.googleapis.com/v1/speech:recognize?key=GOOGLE-KEY", requestJson);
                if (response.IsSuccessStatusCode)
                {
                    var content = await response.Content.ReadAsStringAsync();

                    var converted = JsonConvert.DeserializeObject<GcpSpeechApiResponseModel>(content);

                    if (converted != null) {
                        foreach (var result in converted.Results)
                        {
                            foreach (var alternative in result.Alternatives)
                            {
                                speechToText = speechToText + alternative.Transcript;
                            }
                        }
                    }
                }

                return speechToText;