nil check in refreshHandler + refreshHandler code refactoring (#165)

1) added a nil check in refreshHandler to prevent panic when token is nil, this is when there is no JWT in cookie

2) refactored code to new RefreshToken func, for ppl who like to refresh everytime in Authorization or every request

3) refactored code to new CheckIfTokenExpire func, for ppl who like to only check if token is expired in Authorization, mainly for SPA use, one way to refresh is to only refresh on application load

auth_jwt.go

@@ -438,14 +438,20 @@ func (mw *GinJWTMiddleware) signedString(token *jwt.Token) (string, error) {
 // Shall be put under an endpoint that is using the GinJWTMiddleware.
 // Reply will be of the form {"token": "TOKEN"}.
 func (mw *GinJWTMiddleware) RefreshHandler(c *gin.Context) {
-	token, _ := mw.ParseToken(c)
-	claims := token.Claims.(jwt.MapClaims)
+	tokenString, expire, err := mw.RefreshToken(c)
+	if err != nil {
+		mw.unauthorized(c, http.StatusUnauthorized, mw.HTTPStatusMessageFunc(err, c))
+		return
+	}
 
-	origIat := int64(claims["orig_iat"].(float64))
+	mw.RefreshResponse(c, http.StatusOK, tokenString, expire)
+}
 
-	if origIat < mw.TimeFunc().Add(-mw.MaxRefresh).Unix() {
-		mw.unauthorized(c, http.StatusUnauthorized, mw.HTTPStatusMessageFunc(ErrExpiredToken, c))
-		return
+// RefreshToken refresh token and check if token is expired
+func (mw *GinJWTMiddleware) RefreshToken(c *gin.Context) (string, time.Time, error) {
+	claims, err := mw.CheckIfTokenExpire(c)
+	if err != nil {
+		return "", time.Now(), ErrExpiredToken
 	}
 
 	// Create the token
@@ -462,8 +468,7 @@ func (mw *GinJWTMiddleware) RefreshHandler(c *gin.Context) {
 	tokenString, err := mw.signedString(newToken)
 
 	if err != nil {
-		mw.unauthorized(c, http.StatusUnauthorized, mw.HTTPStatusMessageFunc(ErrFailedTokenCreation, c))
-		return
+		return "", time.Now(), err
 	}
 
 	// set cookie
@@ -480,7 +485,25 @@ func (mw *GinJWTMiddleware) RefreshHandler(c *gin.Context) {
 		)
 	}
 
-	mw.RefreshResponse(c, http.StatusOK, tokenString, expire)
+	return tokenString, expire, nil
+}
+
+// CheckIfTokenExpire check if token expire
+func (mw *GinJWTMiddleware) CheckIfTokenExpire(c *gin.Context) (jwt.MapClaims, error) {
+	token, err := mw.ParseToken(c)
+	if err != nil {
+		return nil, err
+	}
+
+	claims := token.Claims.(jwt.MapClaims)
+
+	origIat := int64(claims["orig_iat"].(float64))
+
+	if origIat < mw.TimeFunc().Add(-mw.MaxRefresh).Unix() {
+		return nil, ErrExpiredToken
+	}
+
+	return claims, nil
 }
 
 // TokenGenerator method that clients can use to get a jwt token.