Add translation example (#1394)

Co-authored-by: nodivbyzero <nodivbyzero@gmail.com>

Author: cxlblm

_examples/http-transalations/main.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+	"strings"
+
+	"github.com/go-playground/locales/en"
+	"github.com/go-playground/locales/zh"
+	"github.com/go-playground/locales/zh_Hant_TW"
+	ut "github.com/go-playground/universal-translator"
+	"github.com/go-playground/validator/v10"
+	en_translations "github.com/go-playground/validator/v10/translations/en"
+	zh_translations "github.com/go-playground/validator/v10/translations/zh"
+	zh_tw_translations "github.com/go-playground/validator/v10/translations/zh_tw"
+)
+
+var uni *ut.UniversalTranslator
+
+// This example showcases how to use the Validator and UniversalTranslator with both Simplified and Traditional Chinese languages.
+// To run the example:
+// Step 1: go run _examples/http-transalations/main.go
+// Step 2 - Simplified Chinese: curl -d '{"first_name":"foo"}' -H "Accept-Language: zh" -H "Content-Type: application/json" -X POST http://localhost:8081/users
+// Step 3 - Traditional Chinese: curl -d '{"first_name":"foo"}' -H "Accept-Language: zh-Hant-TW" -H "Content-Type: application/json" -X POST http://localhost:8081/users
+func main() {
+	validate := validator.New()
+	en := en.New()
+	uni = ut.New(en, en, zh.New(), zh_Hant_TW.New())
+
+	validate = validator.New()
+	enTrans, _ := uni.GetTranslator("en")
+	en_translations.RegisterDefaultTranslations(validate, enTrans)
+	zhTrans, _ := uni.GetTranslator("zh")
+	zh_translations.RegisterDefaultTranslations(validate, zhTrans)
+	zhHantTrans, _ := uni.GetTranslator("zh_Hant_TW")
+	zh_tw_translations.RegisterDefaultTranslations(validate, zhHantTrans)
+
+	type User struct {
+		FirstName string `json:"first_name" validate:"required"`
+		LastName  string `json:"last_name" validate:"required"`
+	}
+
+	http.HandleFunc("/users", func(w http.ResponseWriter, r *http.Request) {
+		// ... fill user value
+		var user User
+
+		// Header Accept-Language value is en or zh
+		trans, _ := uni.GetTranslator(strings.Replace(r.Header.Get("Accept-Language"), "-", "_", -1))
+		if err := validate.Struct(&user); err != nil {
+			var errs validator.ValidationErrors
+			var httpErrors []validator.ValidationErrorsTranslations
+			if errors.As(err, &errs) {
+				httpErrors = append(httpErrors, errs.Translate(trans))
+			}
+			r, _ := json.Marshal(httpErrors)
+			w.Write(r)
+		}
+	})
+
+	http.ListenAndServe(":8081", nil)
+}