rsnext/examples/with-lingui/components/LangSwitcher.js

import Router from 'next/router'
import { I18n } from '@lingui/react'
import { t, Trans } from '@lingui/macro'

const availableLanguageNames = {
  'en': t`English`,
  'sv': t`Swedish`
}
const availableLanguages = Object.keys(availableLanguageNames)

export default () => {
  function onSubmit (evt) {
    evt.preventDefault()
    Router.push({
      pathname: window.location.pathname,
      query: { lang: evt.currentTarget.lang.value }
    })
  }

  return (
    <I18n>{({ i18n }) =>
      <form onSubmit={onSubmit}>
        <select key={i18n.language} name='lang' defaultValue={availableLanguages.find(lang => lang !== i18n.language)}>
          {availableLanguages.map(lang => (
            <option key={lang} value={lang} disabled={i18n.language === lang}>{i18n._(availableLanguageNames[lang])}</option>
          ))}
        </select>
        <button><Trans>Switch language</Trans></button>
      </form>
    }</I18n>
  )
}