Golang web app localization

I have a web app written in golang, and I am planning to make it available in more than one language, I've taken a look at multiple available l18n packages but some things were not clear to me.

What packages would be ideal to determine the users locale and load the site accordingly? Like from browser preferences or location?

You can use https://github.com/nicksnyder/go-i18n/

Then in your project you have to create a folder called i18n/ and use a function like this:

import (
	"fmt"
	"io/ioutil"

	"github.com/nicksnyder/go-i18n/i18n"
)

func loadI18nFiles() {
	files, _ := ioutil.ReadDir("i18n")
	exists := false

	for _, file := range files {
		if err := i18n.LoadTranslationFile(fmt.Sprintf("i18n/%s", file.Name())); err != nil {
			log.Errorf("i18n: error loading file %s. err: %s", file.Name(), err)
		} else {
			log.Infof("i18n: lang file %s loaded", file.Name())
		}

        # Check if you have a default language
		if file.Name() == fmt.Sprintf("%s.json", "en-US") {
			exists = true
		}
	}

	if !exists {
		panic(fmt.Sprintf("Hey! You can't use a default language (%s) that doesn't exists on i18n folder", props.DefaultLang))
	}
}

Then to use, import the package and call the function:

T, _ := i18n.Tfunc("es-AR", "en-US")

fmt.Printf(T("key"))

Each file inside i18n folder is a .json

Example:

en-US.json

[
  {
    "id": "key",
    "translation": "Hello World"
  }
]

es-AR.json

[
  {
    "id": "key",
    "translation": "Hola Mundo"
  }
]