Extract error consts

jwt/login.go

@@ -44,11 +44,17 @@ func (tv *TokenVerifier) CreateToken(user *postgres.User) (string, error) {
 	return t, nil
 }
 
+var (
+	ErrUnexpectedSigningMethod = fmt.Errorf("Unexpected signing method")
+	ErrInvalidToken            = fmt.Errorf("Token is invalid")
+	ErrTokenExpired            = fmt.Errorf("Token has expired")
+)
+
 // VerifyToken verifys a given string-token
 func (tv *TokenVerifier) VerifyToken(tokenString string) (budgeteer.Token, error) {
 	token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
 		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
-			return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
+			return nil, fmt.Errorf("method '%v': %w", token.Header["alg"], ErrUnexpectedSigningMethod)
 		}
 		return []byte(secret), nil
 	})
@@ -72,16 +78,16 @@ func (tv *TokenVerifier) VerifyToken(tokenString string) (budgeteer.Token, error
 
 func verifyToken(token *jwt.Token) (jwt.MapClaims, error) {
 	if !token.Valid {
-		return nil, fmt.Errorf("Token is not valid")
+		return nil, ErrInvalidToken
 	}
 
 	claims, ok := token.Claims.(jwt.MapClaims)
 	if !ok {
-		return nil, fmt.Errorf("Claims are not of Type MapClaims")
+		return nil, ErrInvalidToken
 	}
 
 	if !claims.VerifyExpiresAt(time.Now().Unix(), true) {
-		return nil, fmt.Errorf("Claims have expired")
+		return nil, ErrTokenExpired
 	}
 
 	return claims, nil