go get github.com/astaxie/beego/validation

go test github.com/astaxie/beego/validation

import (
	"github.com/astaxie/beego/validation"
	"log"
)

type User struct {
	Name string
	Age int
}

func main() {
	u := User{"man", 40}
	valid := validation.Validation{}
	valid.Required(u.Name, "name")
	valid.MaxSize(u.Name, 15, "nameMax")
	valid.Range(u.Age, 0, 140, "age")
	if valid.HasErrors() {
		// validation does not pass
		// print invalid message
		for _, err := range valid.Errors {
			log.Println(err.Key, err.Message)
		}
	}
	// or use like this
	if v := valid.Max(u.Age, 140, "ageMax"); !v.Ok {
		log.Println(v.Error.Key, v.Error.Message)
	}
}

import (
	"github.com/astaxie/beego/validation"
)

// validation function follow with "valid" tag
// functions divide with ";"
// parameters in parentheses "()" and divide with ","
// Match function's pattern string must in "//"
type user struct {
	Id   int
	Name string `valid:"Required;Match(/^(test)?\\w*@;com$/)"`
	Age  int    `valid:"Required;Range(1, 140)"`
}

func main() {
	valid := validation.Validation{}
	// ignore empty field valid
	// see CanSkipFuncs
	// valid := validation.Validation{RequiredFirst:true}
	u := user{Name: "test", Age: 40}
	b, err := valid.Valid(u)
	if err != nil {
		// handle error
	}
	if !b {
		// validation does not pass
		// blabla...
	}
}

import (
	"github.com/astaxie/beego/validation"
)

type user struct {
	Id   int
	Name string `valid:"Required;IsMe"`
	Age  int    `valid:"Required;Range(1, 140)"`
}

func IsMe(v *validation.Validation, obj interface{}, key string) {
	name, ok:= obj.(string)
	if !ok {
		// wrong use case?
		return
	}

	if name != "me" {
		// valid false
		v.SetError("Name", "is not me!")
	}
}

func main() {
	valid := validation.Validation{}
	if err := validation.AddCustomFunc("IsMe", IsMe); err != nil {
		// hadle error
	}
	u := user{Name: "test", Age: 40}
	b, err := valid.Valid(u)
	if err != nil {
		// handle error
	}
	if !b {
		// validation does not pass
		// blabla...
	}
}

Required
Min(min int)
Max(max int)
Range(min, max int)
MinSize(min int)
MaxSize(max int)
Length(length int)
Alpha
Numeric
AlphaNumeric
Match(pattern string)
AlphaDash
Email
IP
Base64
Mobile
Tel
Phone
ZipCode