google apps script - HtmlService.createHtmlOutputFromFile can't find file -

google apps script - HtmlService.createHtmlOutputFromFile can't find file -

i trying create web app script , publish web site. @ first experimental level want doget function execute

htmlservice.createhtmloutputfromfile('mypage')

and "not found" error.

mypage simple html file outputs "hello world". if alter script

htmlservice.createhtmloutput('hello world')

the code executes fine when url linked. appears html file created doget function access , output can't found although have saved , saved version of project includes it. can give me hint?

it not need extension. need html file created file > new html file.

google-apps-script