How to get data from a RESTful API with dialogflow

You need to return Promise like

function dialogflowHanlderWithRequest(agent) {
  return new Promise((resolve, reject) => {
    request.get(options, (error, response, body) => {
      JSON.parse(body)
      // processing code
      agent.add(...)
      resolve();
    });
  });
};

See following for details:

Dialogflow NodeJs Fulfillment V2 - webhook method call ends before completing callback

If this works in another application then I believe you're getting an error because you're attempting to access an external resource while using Firebases free Spark plan, which limits you to Google services only. You will need to upgrade to the pay as you go Blaze plan to perform Outbound networking tasks.

Due to asynchronicity, the function go() is gonna be called after the callback of callapi been executed.

Although you said that you have tried to use async, I suggest the following changes that are more likely to work in your scenario:

app.intent(GetData, async (conv) => {
    var test= "error";

    apicaller.callApi(async answer =>
      {
        test = answer.people[0].name
        await go()

      })
      async function go ()
      {
      conv.ask(`No matter what people tell you, words and ideas change the world ${test}`)
      }

First follow the procedure given in their Github repository

https://github.com/googleapis/nodejs-dialogflow

Here you can find a working module already given in the README file. You have to make keyFilename object to store in SessionsClient object creation (go at the end of post to know how to genearate credentials file that is keyFileName). Below the working module.

const express = require("express");

const bodyParser = require("body-parser");

const app = express();

app.use(bodyParser.urlencoded({ extended: true }));

app.use(bodyParser.json());

//////////////////////////////////////////////////////////////////
const dialogflow = require("dialogflow");
const uuid = require("uuid");

/**
 * Send a query to the dialogflow agent, and return the query result.
 * @param {string} projectId The project to be used
 */
async function runSample(projectId = "<your project Id>") {
  // A unique identifier for the given session
  const sessionId = uuid.v4();

  // Create a new session
  const sessionClient = new dialogflow.SessionsClient({
    keyFilename: "<The_path_for_your_credentials_file>"
  });
  const sessionPath = sessionClient.sessionPath(projectId, sessionId);

  // The text query request.
  const request = {
    session: sessionPath,
    queryInput: {
      text: {
        // The query to send to the dialogflow agent
        text: "new page",
        // The language used by the client (en-US)
        languageCode: "en-US"
      }
    }
  };

  // Send request and log result
  const responses = await sessionClient.detectIntent(request);
  console.log("Detected intent");
  console.log(responses);
  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.`);
  }
}

runSample();

Here you can obtain the keyFileName file that is the credentials file using google cloud platform using

https://cloud.google.com/docs/authentication/getting-started

For complete tutorial (Hindi language) watch youtube video:

https://www.youtube.com/watch?v=aAtISTrb9n4&list=LL8ZkoggMm9re6KMO1IhXfkQ