vue.config.js

const path = require('path');

module.exports = {
  publicPath: '',
  chainWebpack: config => {
    const apiClient = process.env.VUE_APP_API_CLIENT // mock or server
    config.resolve.alias.set(
      'api-client',
      path.resolve(__dirname, `src/api/${apiClient}`)
    )
  }
}