How to Implement Request Validation in Go

Use the github.com/go-playground/validator library to define validation rules on struct fields and run them via validator.Validate.

package main

import (
	"fmt"
	"github.com/go-playground/validator/v10"
)

type User struct {
	Name  string `validate:"required,min=3,max=50"`
	Email string `validate:"required,email"`
	Age   int    `validate:"gte=18,lte=120"`
}

func main() {
	validate := validator.New()
	user := User{Name: "A", Email: "invalid", Age: 15}

	if err := validate.Struct(user); err != nil {
		fmt.Println("Validation failed:", err)
		return
	}
	fmt.Println("Validation passed")
}

Install the library with go get github.com/go-playground/validator/v10.

Request validation checks that incoming data matches your expected format before your code processes it. It prevents errors and security issues by rejecting bad inputs like empty names or invalid emails immediately. Think of it as a bouncer at a club who checks IDs before letting anyone inside.