Reduce spurious error messages in test suite.

Prevent the possibility of closing the server socket
before calling net/accept-loop in net/server by adding
a call to (ev/sleep 0).

src/boot/boot.janet

@@ -4309,8 +4309,12 @@
     (assert (not (and (= cntype :datagram) handler))
             "handler not supported for :datagram servers")
     (def s (net/listen host port cntype no-reuse))
-    (if handler
-      (ev/go (fn :net/server-handler [] (net/accept-loop s handler))))
+    (when handler
+      (ev/go (fn :net/server-handler [] (net/accept-loop s handler)))
+      # Ensure accept-loop has started before returning. Not completely needed, but avoids
+      # the possibility of closing `s` before `net/accept-loop` runs
+      # and getting an annoying error print from `:net/server-handler`
+      (ev/sleep 0))
     s))
 
 ###

test/suite-ev.janet

@@ -489,7 +489,7 @@
 (defn level-trigger-handling [conn &] (:close conn))
 (def s (assert (net/server test-host test-port level-trigger-handling)))
 (def c (assert (net/connect test-host test-port)))
-(:close s)
+(:close s) # closing s before net/server's accept loop starts.
 
 # Issue #1531 no. 2
 (def c (ev/chan 0))