It's not true that Go can't add new keywords. Now that we have Go modules, all Go code is now explicitly annotated with the version of Go it was written against

It's not true that Go can't add new keywords. Now that we have Go modules, all Go code is now explicitly annotated with the version of Go it was written against. We can add a new keyword in a later version of Go as long as the compiler can still also compile code written for the older versions of Go. (The go command tells the compiler which version of Go to use for each package it compiles.) What we're not going to do is abandon all the code written for older versions of Go, like Python 3 or Perl 6 did. Python is recovering now but it easily lost a decade to the Python 2 -> Python 3 transition, almost certainly unnecessarily. And Perl lost even more.