Add documentation for a shutdown hook (#174)

docs/Basics.md

@@ -64,3 +64,31 @@ main =
   HTTPure.serveSecure' customSSLOptions customOptions router $
     Console.log "Server up"
 ```
+
+## Shutdown hook
+
+To gracefully shut down a server you can add a shutdown hook. For this you will need to add the following dependencies:
+```
+posix-types
+node-process
+``` 
+
+Then take the closing handler returned by `serve` and create a `SIGINT` and `SIGTERM` hook:
+
+```purescript
+import Prelude
+
+import Data.Posix.Signal (Signal(..))
+import Effect (Effect)
+import Effect.Console as Console
+import HTTPure as HTTPure
+import Node.Process (onSignal)
+
+main :: Effect Unit
+main = do 
+  closingHandler <- HTTPure.serve 8080 (const $ HTTPure.ok "hello world!") do
+    Console.log $ "Server now up on port 8080"
+
+  onSignal SIGINT $ closingHandler $ Console.log "Received SIGINT, stopping service now."  
+  onSignal SIGTERM $ closingHandler $ Console.log "Received SIGTERM, stopping service now."  
+```