Add graceful shutdown handler for SIGINT and SIGTERM.

src/short_url.nim

@@ -1,4 +1,4 @@
-import std/[json, nre, sequtils, strutils]
+import std/[json, nre, posix, sequtils, strutils]
 import cliutils, docopt, mummy, namespaced_logging
 import webby/httpheaders
 
@@ -91,6 +91,11 @@ when isMainModule:
     elif args["--debug"]: logSvc.setRootThreshold(lvlDebug)
 
     let server = newServer(makeHandler(cfg.mappings, logSvc))
+
+    onSignal(SIGINT, SIGTERM):
+      logger.info("short_url shutting down")
+      server.close()
+
     logger.info("short_url v$# listening for requests on $#" %
       [ VERSION, $cfg.port ])
     server.serve(Port(cfg.port), address = "0.0.0.0")