core.clj

(ns rgm.core
    (:require [clojure.core.async :as a]))

  (def c (a/chan))

  (def consumer
    (a/go-loop
     [a 0]
     (let [b (a/<! c)]
       (prn "in loop" a b)
       (recur b))))

  (comment

   (a/put! c 5)
   (a/put! c 6)

   )

repl.txt

rgm@netherton 201907-async-prn % clj -A:rgm/nrepl
nREPL server started on port 52750 on host localhost - nrepl://localhost:52750
nREPL 0.7.0-alpha1
Clojure 1.10.1
OpenJDK 64-Bit Server VM 12.0.1+12
Interrupt: Control+C
Exit:      Control+D or (exit) or (quit)
user=> (require '[clojure.core.async :as a])
nil
user=> (require 'rgm.core :reload)
nil
user=> (a/put! rgm.core/c 10)
true
user=>