refactor(Main): simplify the getPort function by using readJSON_

Documentation:
https://pursuit.purescript.org/packages/purescript-simple-json/7.0.0/docs/Simple.JSON#v:readJSON_

src/Main.purs

@@ -5,25 +5,21 @@ import Prelude
 import Data.Either (Either(..))
 import Data.Maybe (Maybe(..))
 import Effect (Effect)
-import Foreign (MultipleErrors)
 import HTTP.Server as HTTPServer
 import HTTP.Utils as HTTPUtils
 import Logger as Logger
 import Node.Process (lookupEnv)
 import Orchestrator.FS (readFile)
 import Orchestrator.JSON (fromJSON)
 import Orchestrator.Main (makeId, makeSecret, runDefinitionWithIdAndSecret)
-import Simple.JSON (readJSON)
+import Simple.JSON (readJSON_)
 
 getPort :: Effect Int
 getPort = do
  maybePort <- lookupEnv "PORT"
- case maybePort of
+ case (maybePort >>= readJSON_) of
  Nothing -> pure 8181
- (Just portString) -> do
- case (readJSON portString :: Either MultipleErrors Int) of
- (Left _) -> pure 8181
- (Right port) -> pure port
+ (Just port) -> pure port
 
 main :: Effect Unit
 main = do