postcss.config.js

const fs = require('fs')
const path = require('path')
const { CachedInputFileSystem, ResolverFactory } = require('enhanced-resolve')

const myResolver = ResolverFactory.createResolver({
    alias: {
        '@': path.resolve(__dirname, './lib/client/src')
    },
    preferRelative: true,
    fileSystem: new CachedInputFileSystem(fs, 4000),
    useSyncFileSystemCalls: true,
    extensions: ['.css']
})

module.exports = {
    plugins: [
        [
            'postcss-import',
            {
                resolve (id, baseDir) {
                    return myResolver.resolveSync({}, baseDir, id)
                }
            }
        ],
        'postcss-simple-vars',
        'postcss-mixins',
        'postcss-nested-ancestors',
        'postcss-nested',
        'postcss-preset-env',
        'postcss-url'
    ]
}