This file contains two function to create and sign JWT token, the generation needs a token which is declared global in file but token key passes to check function

golang-jwt-example.go

package cryptoUtils

import (
	"github.com/dgrijalva/jwt-go"
	"time"
)

type Credentials struct {
	Password string `json:"password"`
	Username string `json:"username"`
}

// TODO: register all tokens at environmental variables
var JWTKey = []byte("ServerToken")

// Create a struct that will be encoded to a JWT.
// We add jwt.StandardClaims as an embedded type, to provide fields like expiry time
type Claims struct {
	Username string `json:"username"`
	jwt.StandardClaims
}

func generateJWT(username string) (string, error) {
	// Declare the expiration time of the token
	// here, we have kept it as 5 minutes
	expirationTime := time.Now().Add(5 * time.Minute)
	// Create the JWT claims, which includes the username and expiry time
	claims := &Claims{
		Username: username,
		StandardClaims: jwt.StandardClaims{
			// In JWT, the expiry time is expressed as unix milliseconds
			ExpiresAt: expirationTime.Unix(),
		},
	}

	// Declare the token with the algorithm used for signing, and the claims
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	// Create the JWT string
	return token.SignedString(JWTKey)
}

func CheckJWTToken(tknStr string, jwtKey []byte) error {
	claims := &Claims{}
	// Parse the JWT string and store the result in `claims`.
	// Note that we are passing the key in this method as well. This method will return an error
	// if the token is invalid (if it has expired according to the expiry time we set on sign in),
	// or if the signature does not match
	_, err := jwt.ParseWithClaims(tknStr, claims, func(token *jwt.Token) (interface{}, error) {
		return jwtKey, nil
	})
	if err != nil {
		return err
	}
	return nil
}