Can't override index.html


I’m trying to add Google API into my IONIC project. I tried to added this script into www/index.html

<script src=""

This script worked but each time I run ionic serve or ionic cordova run android, this script is removed from index.html
This is my IONIC info

cli packages: (/usr/lib/node_modules)

    @ionic/cli-utils  : 1.13.1
    ionic (Ionic CLI) : 3.13.2

global packages:

    cordova (Cordova CLI) : 7.1.0 

local packages:

    @ionic/app-scripts : 3.0.1
    Cordova Platforms  : android 6.3.0
    Ionic Framework    : ionic-angular 3.7.1


    Android SDK Tools : 26.1.1
    Node              : v6.11.4
    npm               : 3.10.10 
    OS                : Linux 4.10


    backend : pro


Amend index.html in src
Never amend stuff in www
All that gets generated and overwritten