Add ev/call.

This is a common operation, and making fibers manually can be tedious.

examples/tcpserver.janet

@@ -1,27 +1,17 @@
 (defn handler
   "Simple handler for connections."
   [stream]
-  (def id (gensym))
-  (def b @"")
-  (print "Connection " id "!")
-  (while (:read stream 1024 b)
-    (repeat 10 (print "work for " id " ...") (ev/sleep 1))
-    (:write stream b)
-    (buffer/clear b))
-  (printf "Done %v!" id))
-
-(defn spawn-kid
-  "Run handler in a new fiber"
-  [conn]
-  (def f (fiber/new handler))
-  (ev/go f conn))
-
-(print "Starting echo server on 127.0.0.1:8000")
-
-(def server (net/server "127.0.0.1" "8000"))
+  (defer (:close stream)
+    (def id (gensym))
+    (def b @"")
+    (print "Connection " id "!")
+    (while (:read stream 1024 b)
+      (repeat 10 (print "work for " id " ...") (ev/sleep 1))
+      (:write stream b)
+      (buffer/clear b))
+    (printf "Done %v!" id)))
 
 # Run server.
-(while true
-  (with [conn (:accept server)]
-    (spawn-kid conn)
-    (ev/sleep 0.1)))
+(let [server (net/server "127.0.0.1" "8000")]
+  (print "Starting echo server on 127.0.0.1:8000")
+  (while true (ev/call handler (:accept server))))