Webpack resolve extensions not working with SSR

[Priya Pandian]

I have 2 set of files .custom.js and .js and I want the .custom.js take the higher precedence over the default .js extension. So I added in the module export part as

resolve: {
extensions: ['.custom.js', '.js', '.json']
}

This is working fine in the client side.

But after adding the webpack-isomorphic-tools code, it's always taking the default extension and the resolve extension is not getting considered.

Can someone help me with this ?

Webpack : 4.18.0
Webpack isomorphic tools: 3.0.6
Babel : @babel/core - 7.0.0