Here is how I do with typescript:

import * as fs from 'fs'
import * as _ from "lodash"

const TEMPLATE_SETTINGS = {
    interpolate: /{{([\s\S]+?)}}/g, // Mustache template delimiter: `{{variable}}`
    evaluate: undefined, 
    escape: undefined, 
}

const value = _.template(fs.readFileSync('./assets/file.yaml', 'utf8'), TEMPLATE_SETTINGS)({
                var1: 'value1',                     
                var2: 'value2',
            })

see doc of lodash interpolate for more details

as there is no pulumi way today (I guess), we have to use language capabilities

and it could be great to have these workarounds in doc 😉

note that I use mustache delimiter to prevent conflict with bash variable (

$VAR

)

I am ysing type script 🙂