Updated to chapter 3

package.yaml

@@ -22,6 +22,8 @@ description:         Please see the README on GitHub at <https://github.com/gith
 dependencies:
 - base >= 4.7 && < 5
 - warp >= 3.2.28 && < 4
+- wai >= 3.2.2.1 && < 4
+- http-types >= 0.12.3 && < 0.13
 
 library:
   source-dirs: src

src/Lib.hs

+{-# LANGUAGE OverloadedStrings #-}
+
 module Lib
     ( someFunc
     ) where
 
+import Network.Wai.Handler.Warp (run)
+import Network.Wai (Request, Response, ResponseReceived, responseLBS)
+import Network.HTTP.Types.Status (status200)
+
 someFunc :: IO ()
-someFunc = do
-  someValue <- return "Hello, Monad!"
-  putStrLn someValue
+someFunc = run 8080 requestHandler
+
+requestHandler :: Request -> (Response -> IO ResponseReceived) -> IO ResponseReceived
+requestHandler request respond =
+  let
+    response = responseLBS status200 [] "Hello, client!"
+  in
+    do
+      putStrLn "Received an HTTP request!"
+      respond response