This program never exits. Which part of Clojure's concurrency am I not understanding?

core.clj

(ns test.core
  (:gen-class))

(def AGENT (agent "foo"))

(defn do-thing [a b]
  (str a "=" b))

(defn -main
  ""
  [& args]
  (println "Hello, World!")

  (send-off AGENT do-thing "bar")
  (await-for 3000 AGENT)
  (println @AGENT)

  (println "Done!"))

shell

$ java  -jar target/test-0.1.0-SNAPSHOT-standalone.jar
Hello, World!
foo=bar
Done!

[never returns]

thread dump

Full thread dump Java HotSpot(TM) 64-Bit Server VM (20.51-b01-457 mixed mode):

"DestroyJavaVM" prio=5 tid=7fdec2953800 nid=0x10db5d000 waiting on condition [00000000]
   java.lang.Thread.State: RUNNABLE

"clojure-agent-send-pool-0" prio=5 tid=7fdec2953000 nid=0x1161dc000 waiting on condition [1161db000]
   java.lang.Thread.State: WAITING (parking)
  at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <7f38b1088> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
	at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:1987)
	at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:399)
	at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:957)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:917)
	at java.lang.Thread.run(Thread.java:680)

"Low Memory Detector" daemon prio=5 tid=7fdec401a800 nid=0x115357000 runnable [00000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" daemon prio=9 tid=7fdec4019800 nid=0x115254000 waiting on condition [00000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" daemon prio=9 tid=7fdec4019000 nid=0x115151000 waiting on condition [00000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" daemon prio=9 tid=7fdec4018000 nid=0x11504e000 waiting on condition [00000000]
   java.lang.Thread.State: RUNNABLE

"Surrogate Locker Thread (Concurrent GC)" daemon prio=5 tid=7fdec4017800 nid=0x114f4b000 waiting on condition [00000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" daemon prio=8 tid=7fdec4006800 nid=0x114cbd000 in Object.wait() [114cbc000]
   java.lang.Thread.State: WAITING (on object monitor)
	at java.lang.Object.wait(Native Method)
	- waiting on <7f42b02e8> (a java.lang.ref.ReferenceQueue$Lock)
	at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118)
	- locked <7f42b02e8> (a java.lang.ref.ReferenceQueue$Lock)
	at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134)
	at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:171)

"Reference Handler" daemon prio=10 tid=7fdec4006000 nid=0x114bba000 in Object.wait() [114bb9000]
   java.lang.Thread.State: WAITING (on object monitor)
	at java.lang.Object.wait(Native Method)
	- waiting on <7f42b4070> (a java.lang.ref.Reference$Lock)
	at java.lang.Object.wait(Object.java:485)
	at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116)
	- locked <7f42b4070> (a java.lang.ref.Reference$Lock)

"VM Thread" prio=9 tid=7fdec2843800 nid=0x114ab7000 runnable

"Gang worker#0 (Parallel GC Threads)" prio=9 tid=7fdec2000800 nid=0x110f60000 runnable

"Gang worker#1 (Parallel GC Threads)" prio=9 tid=7fdec2001000 nid=0x111063000 runnable

"Gang worker#2 (Parallel GC Threads)" prio=9 tid=7fdec4000800 nid=0x111166000 runnable

"Gang worker#3 (Parallel GC Threads)" prio=9 tid=7fdec4001000 nid=0x111269000 runnable

"Concurrent Mark-Sweep GC Thread" prio=9 tid=7fdec587c800 nid=0x11472f000 runnable
"VM Periodic Task Thread" prio=10 tid=7fdec402c000 nid=0x11545a000 waiting on condition

"Exception Catcher Thread" prio=10 tid=7fdec5801800 nid=0x10dd88000 runnable
JNI global references: 1734

Heap
 par new generation   total 19136K, used 11596K [7f3000000, 7f44c0000, 7f44c0000)
  eden space 17024K,  61% used [7f3000000, 7f3a291e8, 7f40a0000)
  from space 2112K,  56% used [7f42b0000, 7f43da210, 7f44c0000)
  to   space 2112K,   0% used [7f40a0000, 7f40a0000, 7f42b0000)
 concurrent mark-sweep generation total 63872K, used 0K [7f44c0000, 7f8320000, 7fae00000)
 concurrent-mark-sweep perm gen total 21248K, used 12316K [7fae00000, 7fc2c0000, 800000000)

 (shutdown-agents)

rolls eyes