$ curl --location --request post 'http://localhost:8000/hellos' \
→ --header 'content-type: application/json' \
→ --data-raw '(begin
→ (define (fac x)
→ (if (<= x 0) 1 (* x (fac (- x 1)))))
→ (fac 5))'
{"msg":120,"code":200}