How do I set the language in the racket REPL

Question

I would like to set the language that my racket REPL is using interactively, like this:

-> #lang typed/racket
; readline-input:15:0: read: #lang not enabled in the current context [,bt for
;   context]
; typed/racket: undefined;
;  cannot reference undefined identifier
; [,bt for context]`

But it gives me this error:

-> ,bt
; typed/racket: undefined;
;  cannot reference undefined identifier

What is my error?

Answer 1

From the terminal you can choose what language to use when you start racket:

racket -I typed/racket