Validate golang request data with simple rules. Highly inspired by Laravel's request validation.

Install the package using

$ go get github.com/thedevsaddam/govalidator
// or
$ go get gopkg.in/thedevsaddam/govalidator.v1

To use the package import it in your *.go code

import "github.com/thedevsaddam/govalidator"
// or
import "gopkg.in/thedevsaddam/govalidator.v1"

Validate form-data, x-www-form-urlencoded and query params

package main

import (
	"encoding/json"
	"fmt"
	"net/http"

	"github.com/thedevsaddam/govalidator"
)

func handler(w http.ResponseWriter, r *http.Request) {
	rules := govalidator.MapData{
		"username": []string{"required", "between:3,8"},
		"email":    []string{"required", "min:4", "max:20", "email"},
		"web":      []string{"url"},
		"phone":    []string{"digits:11"},
		"agree":    []string{"bool"},
		"dob":      []string{"date"},
	}

	messages := govalidator.MapData{
		"username": []string{"required:আপনাকে অবশ্যই ইউজারনেম দিতে হবে", "between:ইউজারনেম অবশ্যই ৩-৮ অক্ষর হতে হবে"},
		"phone":    []string{"digits:ফোন নাম্বার অবশ্যই ১১ নম্বারের হতে হবে"},
	}

	opts := govalidator.Options{
		Request:         r,        // request object
		Rules:           rules,    // rules map
		Messages:        messages, // custom message map (Optional)
		RequiredDefault: true,     // all the field to be pass the rules
	}
	v := govalidator.New(opts)
	e := v.Validate()
	err := map[string]interface{}{"validationError": e}
	w.Header().Set("Content-type", "application/json")
	json.NewEncoder(w).Encode(err)
}

func main() {
	http.HandleFunc("/", handler)
	fmt.Println("Listening on port: 9000")
	http.ListenAndServe(":9000", nil)
}

Send request to the server using curl or postman: curl GET "http://localhost:9000?web=&phone=&zip=&dob=&agree="

Response

{
    "validationError": {
        "agree": [
            "The agree may only contain boolean value, string or int 0, 1"
        ],
        "dob": [
            "The dob field must be a valid date format. e.g: yyyy-mm-dd, yyyy/mm/dd etc"
        ],
        "email": [
            "The email field is required",
            "The email field must be a valid email address"
        ],
        "phone": [
            "ফোন নাম্বার অবশ্যই ১১ নম্বারের হতে হবে"
        ],
        "username": [
            "আপনাকে অবশ্যই ইউজারনেম দিতে হবে",
            "ইউজারনেম অবশ্যই ৩-৮ অক্ষর হতে হবে"
        ],
        "web": [
            "The web field format is invalid"
        ]
    }
}

Validate file

• Validate file

Validate application/json or text/plain as raw body

• Validate JSON to simple struct
• Validate JSON to map
• Validate JSON to nested struct
• Validate using custom rule

Validate struct directly

• Validate Struct

• alpha The field under validation must be entirely alphabetic characters.
• alpha_dash The field under validation may have alpha-numeric characters, as well as dashes and underscores.
• alpha_space The field under validation may have alpha-numeric characters, as well as dashes, underscores and space.
• alpha_num The field under validation must be entirely alpha-numeric characters.
• between:numeric,numeric The field under validation check the length of characters/ length of array, slice, map/ range between two integer or float number etc.
• numeric The field under validation must be entirely numeric characters.
• numeric_between:numeric,numeric The field under validation must be a numeric value between the range. e.g: numeric_between:18,65 may contains numeric value like 35, 55 . You can also pass float value to check. Moreover, both bounds can be omitted to create an unbounded minimum (e.g: numeric_between:,65) or an unbounded maximum (e.g: numeric_between:-1,).
• bool The field under validation must be able to be cast as a boolean. Accepted input are true, false, 1, 0, "1" and "0".
• credit_card The field under validation must have a valid credit card number. Accepted cards are Visa, MasterCard, American Express, Diners Club, Discover and JCB card
• coordinate The field under validation must have a value of valid coordinate.
• css_color The field under validation must have a value of valid CSS color. Accepted colors are hex, rgb, rgba, hsl, hsla like #909, #00aaff, rgb(255,122,122)
• date The field under validation must have a valid date of format yyyy-mm-dd or yyyy/mm/dd.
• date:dd-mm-yyyy The field under validation must have a valid date of format dd-mm-yyyy.
• digits:int The field under validation must be numeric and must have an exact length of value.
• digits_between:int,int The field under validation must be numeric and must have length between the range. e.g: digits_between:3,5 may contains digits like 2323, 12435
• in:foo,bar The field under validation must have one of the values. e.g: in:admin,manager,user must contain the values (admin or manager or user)
• not_in:foo,bar The field under validation must have one value except foo,bar. e.g: not_in:admin,manager,user must not contain the values (admin or manager or user)
• email The field under validation must have a valid email.
• float The field under validation must have a valid float number.
• mac_address The field under validation must have be a valid Mac Address.
• min:numeric The field under validation must have a min length of characters for string, items length for slice/map, value for integer or float. e.g: min:3 may contains characters minimum length of 3 like "john", "jane", "jane321" but not "mr", "xy"
• max:numeric The field under validation must have a max length of characters for string, items length for slice/map, value for integer or float. e.g: max:6 may contains characters maximum length of 6 like "john doe", "jane doe" but not "john", "jane"
• len:numeric The field under validation must have an exact length of characters, exact integer or float value, exact size of map/slice. e.g: len:4 may contains characters exact length of 4 like Food, Mood, Good
• ip The field under validation must be a valid IP address.
• ip_v4 The field under validation must be a valid IP V4 address.
• ip_v6 The field under validation must be a valid IP V6 address.
• json The field under validation must be a valid JSON string.
• lat The field under validation must be a valid latitude.
• lon The field under validation must be a valid longitude.
• regex:regular expression The field under validation validate against the regex. e.g: regex:^[a-zA-Z]+$ validate the letters.
• required The field under validation must be present in the input data and not empty. A field is considered "empty" if one of the following conditions are true: 1) The value is null. 2)The value is an empty string. 3) Zero length of map, slice. 4) Zero value for integer or float
• size:integer The field under validation validate a file size only in form-data (see example)
• ext:jpg,png The field under validation validate a file extension (see example)
• mime:image/jpg,image/png The field under validation validate a file mime type (see example)
• url The field under validation must be a valid URL.
• uuid The field under validation must be a valid UUID.
• uuid_v3 The field under validation must be a valid UUID V3.
• uuid_v4 The field under validation must be a valid UUID V4.
• uuid_v5 The field under validation must be a valid UUID V5.

func init() {
	// simple example
	govalidator.AddCustomRule("must_john", func(field string, rule string, message string, value interface{}) error {
		val := value.(string)
		if val != "john" || val != "John" {
			return fmt.Errorf("The %s field must be John or john", field)
		}
		return nil
	})

	// custom rules to take fixed length word.
	// e.g: word:5 will throw error if the field does not contain exact 5 word
	govalidator.AddCustomRule("word", func(field string, rule string, message string, value interface{}) error {
		valSlice := strings.Fields(value.(string))
		l, _ := strconv.Atoi(strings.TrimPrefix(rule, "word:")) //handle other error
		if len(valSlice) != l {
			return fmt.Errorf("The %s field must be %d word", field, l)
		}
		return nil
	})

}

Note: Array, map, slice can be validated by adding custom rules.

If you need to translate validation message you can pass messages as options.

messages := govalidator.MapData{
	"username": []string{"required:You must provide username", "between:The username field must be between 3 to 8 chars"},
	"zip":      []string{"numeric:Please provide zip field as numeric"},
}

opts := govalidator.Options{
	Messages:        messages,
}

If you are interested to make the package better please send pull requests or create an issue so that others can fix. Read the contribution guide here

• Jun Kimura
• Steve HIll
• ErickSkrauch
• Sakib Sami
• Rip
• Jose Nazario

The govalidator is an open-source software licensed under the MIT License.