First cut at esm and commonjs

index.cjs

@@ -0,0 +1,57 @@
+const axios = require('axios')
+const { v4: uuid } = require('uuid');
+const md5 = require('md5')
+
+const LIBRARY_VERSION = process.env.npm_package_version || 'unknown'
+const LIBRARY_NAME = process.env.npm_package_name || 'analytics-async'
+
+export async function track(msg) {
+  return call('track', msg)
+}
+
+export async function identify(msg) {
+  return call('identify', msg)
+}
+
+async function call(type, message) {
+
+  message = Object.assign({}, message)
+  message.context = Object.assign({
+    library: {
+      name: LIBRARY_NAME,
+      version: LIBRARY_VERSION
+    }
+  }, message.context)
+
+  message._metadata = Object.assign({
+    nodeVersion: process.versions.node
+  }, message._metadata)
+
+  if (!message.timestamp) {
+    message.timestamp = new Date()
+  }
+
+  if (!message.messageId) {
+    // We md5 the messaage to add more randomness. This is primarily meant
+    // for use in the browser where the uuid package falls back to Math.random()
+    // which is not a great source of randomness.
+    // Borrowed from analytics.js (https://github.com/segment-integrations/analytics.js-integration-segmentio/blob/a20d2a2d222aeb3ab2a8c7e72280f1df2618440e/lib/index.js#L255-L256).
+    message.messageId = `node-${md5(JSON.stringify(message))}-${uuid()}`
+  }
+
+  const headers = {
+    'content-type': 'application/json',
+    'user-agent': `${LIBRARY_NAME}/${LIBRARY_VERSION}`
+  }
+
+  const req = {
+    auth: {
+      username: process.env.SEGMENT_WRITE_KEY || 'Unset process.env.SEGMENT_WRITE_KEY'
+    },
+    headers
+  }
+
+  let p = axios.post(`https://api.segment.io/v1/${type}`, message, req)
+  console.log(`${type} => ${message.userId}`)
+  return p
+}

package.json

@@ -2,7 +2,12 @@
   "name": "analytics-async",
   "version": "0.0.4",
   "description": "The hassle-free way to integrate analytics into any node application w/o dropping API calls.",
-  "main": "index.mjs",
+  "main": "index.js",
+  "type": "module",
+  "exports": {
+    "import": "./main.js",
+    "require": "./main.cjs"
+  },
   "scripts": {
     "start": "node index.mjs",
     "test": "echo \"Error: no test specified\" && exit 1"