GOOPS and fibers - need help understanding what's wrong, bug in fibers/guile?

[Jan Wielkiewicz <tona_kosmicznego_smiecia@interia.pl>]

Hello,

I started writing my project in Guile with GOOPS and fibers (I'll
release it once it stops being a shame and starts working!), but I
encountered a problem:

The example from fibers' manual doesn't work:

(lambda ()
 (spawn-fiber (lambda () (display "hey!\n")))))

It doesn't print "hey" as documented in the manual.
I use guile 3.0.4 and fibers 1.0.0 (from Guix).

I also tried making a simple proof of concept, but it doesn't seem to
do anything. I would like to understand what's wrong with my code or
report a bug, if this is the case. No errors, warnings, syntax errors,
just silence.

My code:

(define-module (blocks block)
  #:use-module (fibers)
  #:use-module (fibers channels)
  #:use-module (oop goops)
  #:use-module (srfi srfi-9) ;; records
  #:export (<peer>
            connect-peers
            send-message
            handle-message
            start-listening))

(define-class <peer> ()
  (input #:init-form '() #:getter get-input
         #:setter set-input #:init-keyword #:input)
  (output #:init-form '() #:getter get-output
          #:setter set-output #:init-keyword #:output))

;; Only connection, no messaging started.
(define-method (connect-peers (p1 <peer>) (p2 <peer>))
  (let ((p1-p2 (make-channel)) ;; p1 to p2
        (p2-p1 (make-channel))) ;; p2 to p1
    (set-input p1 p2-p1)
    (set-output p1 p1-p2)
    (set-input p2 p1-p2)
    (set-output p2 p2-p1)))

(define-method (send-message (p <peer>) msg)
  (put-message (get-output p) msg))

(define-method (handle-message (p <peer>))
  (let loop ()
    (define msg (get-message (get-input p)))
    (match (pk msg)
           ('ping (send-message p 'pong)))
    (loop)))

(define-method (start-listening (p1 <peer>) (p2 <peer>))
  (run-fibers
   (lambda ()
     (spawn-fiber
      (lambda ()
        (connect-peers p1 p2)
        (handle-message p1)
        (send-message p1 'ping)
        (handle-message p2))))))

I run this in repl:

(define p1 (make <peer>))
(define p2 (make <peer>))

(start-listening p1 p2)


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Thanks in advance,
Jan Wielkiewicz