Dynamic values populated from Constants file into Info.plist

I am using a SDK which forces me to add the license key for it in Info.plist with a certain key name but i want to make sure i can dynamically populate those keys from a constant file which i can control and not checkin to my github repo.

Found few articles which talk about this : https://coderwall.com/p/euesdq/use-defined-values-in-info-plist

But doesn't get it to work, i am using Xcode 10 and Swift 4.

Thanks,