lib: return directly from packageMainCache

This commit updates readPackage to return directly when calling
packageMainCache instead of storing the result in a local var
and returning later.

PR-URL: #20591
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

lib/internal/modules/cjs/loader.js

@@ -153,13 +153,12 @@ function readPackage(requestPath) {
   }
 
   try {
-    var pkg = packageMainCache[requestPath] = JSON.parse(json).main;
+    return packageMainCache[requestPath] = JSON.parse(json).main;
   } catch (e) {
     e.path = jsonPath;
     e.message = 'Error parsing ' + jsonPath + ': ' + e.message;
     throw e;
   }
-  return pkg;
 }
 
 function tryPackage(requestPath, exts, isMain) {