What is a JWT token? What is its structure and advantages over regular tokens?

JWT (JSON Web Token) is a compact, URL-safe token for transmitting information between parties in the form of a JSON object. It is often used for authentication and authorization.

JWT Structure: JWT consists of three parts, separated by dots:

1. Header — contains the token type (JWT) and signing algorithm (e.g., HS256).
2. Payload — contains claims, such as user ID, token expiration time.
3. Signature — created by hashing the header and payload with a secret key.

Example JWT:

header.payload.signature

Advantages of JWT over regular tokens:

• Self-contained: contains all necessary information, no need to check a database.
• Security: signature guarantees integrity and authenticity.
• Lightweight transmission: compact and URL-safe format.
• Versatility: can be used across different protocols and platforms.

Example of creating a JWT in Go using the github.com/golang-jwt/jwt library:

import (
    "github.com/golang-jwt/jwt"
    "time"
)

func CreateJWT(secret []byte) (string, error) {
    claims := jwt.MapClaims{
        "user_id": 123,
        "exp": time.Now().Add(time.Hour * 72).Unix(),
    }
    token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
    return token.SignedString(secret)
}