Dialogflow easy way for authorization

I have the same issue few months ago, check this, this is how i solve it. From your JSON that Google Cloud extract this lines.

const dialogflow = require('dialogflow');
const LANGUAGE_CODE = 'en-US'
const projectId = 'projectid';
const sessionId = 'sessionId';
const query = 'text to check';


let privateKey = "private key JSON";
let clientEmail = "email acount from JSON";
let config = {
credentials: {
    private_key: privateKey,
    client_email: clientEmail
}
};

sessionClient = new dialogflow.SessionsClient(config);

async function sendTextMessageToDialogFlow(textMessage, sessionId) {
// Define session path
const sessionPath = this.sessionClient.sessionPath(projectId, sessionId);
// The text query request.
const request = {
    session: sessionPath,
    queryInput: {
        text: {
            text: textMessage,
            languageCode: LANGUAGE_CODE
        }
    }
}
try {
    let responses = await this.sessionClient.detectIntent(request)
    console.log('DialogFlow.sendTextMessageToDialogFlow: Detected intent', responses);
    return responses
} catch (err) {
    console.error('DialogFlow.sendTextMessageToDialogFlow ERROR:', err);
    throw err
}
};


sendTextMessageToDialogFlow(query, sessionId)

I am writing the code, which worked for me. Please follow all the steps provided in Reference link 2 and for coding purpose you can use the snippet provided.

I have also added the sample JSON of Google Cloud Oauth

References:

1. https://www.npmjs.com/package/dialogflow#samples
2. https://medium.com/@tzahi/how-to-setup-dialogflow-v2-authentication-programmatically-with-node-js-b37fa4815d89

//Downloaded JSON format

{
  "type": "service_account",
  "project_id": "mybot",
  "private_key_id": "123456asd",
  "private_key": "YOURKEY",
  "client_email": "[email protected]",
  "client_id": "098091234",
  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
  "token_uri": "https://oauth2.googleapis.com/token",
  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
  "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/yourID%40mybot.iam.gserviceaccount.com"
}


//------*********************---------------------------
//
const projectId = 'mybot';

//https://dialogflow.com/docs/agents#settings
// generate session id (currently hard coded)
const sessionId = '981dbc33-7c54-5419-2cce-edf90efd2170';
const query = 'hello';
const languageCode = 'en-US';

// Instantiate a DialogFlow client.
const dialogflow = require('dialogflow');
let privateKey = 'YourKey';

// as per goolgle json
let clientEmail = "[email protected]";
let config = {
  credentials: {
    private_key: privateKey,
    client_email: clientEmail
  }
}
const sessionClient = new dialogflow.SessionsClient(config);

// Define session path
const sessionPath = sessionClient.sessionPath(projectId, sessionId);

// The text query request.
const request = {
  session: sessionPath,
  queryInput: {
    text: {
      text: query,
      languageCode: languageCode,
    },
  },
};

// Send request and log result
sessionClient
  .detectIntent(request)
  .then(responses => {
    console.log('Detected intent');
    const result = responses[0].queryResult;
    console.log(`  Query: ${result.queryText}`);
    console.log(`  Response: ${result.fulfillmentText}`);
    if (result.intent) {
      console.log(`  Intent: ${result.intent.displayName}`);
    } else {
      console.log(`  No intent matched.`);
    }
  })
  .catch(err => {
    console.error('ERROR:', err);
  });

It is not very well documented, but the easiest way to authenticate is using the JSON file provided on your google cloud platform console.

const sessionClient = new dialogflow.SessionsClient({
    keyFilename: '/path/to/google.json'
});
const sessionPath = sessionClient.sessionPath(projectId, sessionId);

This also works for all the other clients. ContextsClients, EntityTypesClient and so on.