Internationalization

The i18n package loads gettext translations and resolves the best locale per request. It implements the middleware.LocaleProvider seam, so wiring it up makes ProcessLocale — and the renderer’s t/tDefault template functions — work end to end.

Layout and loading

One top-level directory per locale, each containing a default.po:

locales/
├── en/default.po
├── es/default.po
└── pt_BR/default.po

Embed and load it:

//go:embed locales
var localesFS embed.FS

sub, _ := fs.Sub(localesFS, "locales")
locales, err := i18n.Load(sub)               // options: WithDefaultLocale, WithReloading
if err != nil { /* handle */ }

r.Use(middleware.ProcessLocale(locales))

ProcessLocale resolves the locale from the ?lang= query parameter, then the Accept-Language header (full q-list matching via x/text/language, with region fallback — pt-br finds pt_BR). It stores the translator on the context and populates locale, textLanguage, and textDirection (RTL-aware) on the template map.

Using translations in templates

<label>{{ tDefault .locale "Leave a message" "form.label" }}</label>

• tDefault falls back to the given default string when the key is missing — ideal while translations are incomplete.
• t errors on unknown keys — ideal once your catalogs are complete.

With a locales/es/default.po containing:

msgid "form.label"
msgstr "Deja un mensaje"

…requesting /?lang=es renders the Spanish label. The example app demonstrates the full flow.