Release expo app to iOS

1. config app.json

example: 

{
  "expo": {
    "name": "Tech Blog",
    "slug": "tech_blog",
    "privacy" : "public",
    "sdkVersion" : "39.0.0",
    "platforms" : [
      "ios",
      "android"
    ],    
    "version": "4.0.9",
    "orientation": "portrait",
    "icon": "./assets/icon.png",
    "splash": {
      "image": "./assets/splash.png",
      "resizeMode": "contain",
      "backgroundColor": "#ffffff"
    },
    "updates": {
      "fallbackToCacheTimeout": 0
    },
    "assetBundlePatterns": [
      "**/*"
    ],
    "ios": {
      "supportsTablet": true
    },
    "web": {
      "favicon": "./assets/favicon.png"
    }
  }
}

2. to publish to expo is easy, run $ expo publish, you need a free expo account. You can test your build version with expo.

expo publish

3. Once you are good with your build test with expo, build the app packages for iOS / Android store release.

4. Build iOS (your apple developer account is required) :

expo build:ios

4.1 Upload your ios app: 

expo upload:ios

5. Build Android (create new key or using existing key) : 

expo build:android  

or
(if want to use new keystore)
expo build:andriod -c 

or
(if want to build bundle)
expo build:android -t app-bundle

5.1. Upload your app:

expo upload:android