update node docs

Author: silesky

packages/node/README.md

@@ -75,22 +75,16 @@ Here is an example of using analytics.js within a handler:
 ```ts
 const { Analytics } = require('@segment/analytics-node');
 
-// since analytics has the potential to be stateful if there are any plugins added,
-// to be on the safe side, we should instantiate a new instance of analytics on every request (the cost of instantiation is low).
-const analytics = () => new Analytics({
-      flushAt: 1,
+const analytics = new Analytics({
       writeKey: '<MY_WRITE_KEY>',
     })
     .on('error', console.error);
 
 module.exports.handler = async (event) => {
-  ...
-  // we need to await before returning, otherwise the lambda will exit before sending the request.
-  await new Promise((resolve) =>
-    analytics().track({ ... }, resolve)
-   )
+  analytics.track({ ... }) 
+  
+  await analytics.flush()
 
-  ...
   return {
     statusCode: 200,
   };
@@ -105,7 +99,6 @@ import { NextRequest, NextResponse } from 'next/server';
 
 export const analytics = new Analytics({
   writeKey: '<MY_WRITE_KEY>',
-  flushAt: 1,
 })
   .on('error', console.error)
 
@@ -114,9 +107,10 @@ export const config = {
 };
 
 export default async (req: NextRequest) => {
-  await new Promise((resolve) =>
-    analytics.track({ ... }, resolve)
-  );
+  analytics.track({ ... })
+
+  await analytics.flush()
+  
   return NextResponse.json({ ... })
 };
 ```
@@ -125,22 +119,21 @@ export default async (req: NextRequest) => {
 ```ts
 import { Analytics, Context } from '@segment/analytics-node';
 
+const analytics = new Analytics({
+  writeKey: '<MY_WRITE_KEY>',
+}).on('error', console.error);
+
 export default {
   async fetch(
     request: Request,
     env: Env,
     ctx: ExecutionContext
   ): Promise<Response> {
-    const analytics = new Analytics({
-      flushAt: 1,
-      writeKey: '<MY_WRITE_KEY>',
-    }).on('error', console.error);
 
-    await new Promise((resolve, reject) =>
-      analytics.track({ ... }, resolve)
-    );
+    analytics.track({ ... })
+    
+    await analytics.flush()
 
-    ...
     return new Response(...)
   },
 };