Error: "Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema" when opening client dev server

[tamvm]

When starting the dev server, the following error has been printed:
I have tried with two commands to start:

npm start
./node_modules/.bin/webpack-dev-server --open

✖ ｢wds｣: Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.
 - configuration[0] has an unknown property 'mode'. These properties are valid:
   object { amd?, bail?, cache?, context?, dependencies?, devServer?, devtool?, entry, externals?, loader?, module?, name?, node?, output?, parallelism?, performance?, plugins?, profile?, recordsInputPath?, recordsOutputPath?, recordsPath?, resolve?, resolveLoader?, stats?, target?, watch?, watchOptions? }

Anyone has experience with that?
Thank you,

[tamvm]

I come with the solution to use webpack v4 (with some warnings). I hope the core team here update the source code so newbie like me feels no pain in the first glance.