Update Decode Segment and add test case to parser

parser_test.go

@@ -57,6 +57,16 @@ var jwtTestData = []struct {
 		nil,
 		jwt.SigningMethodRS256,
 	},
+	{
+		"basic with padding",
+		"eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJwYWRkZWRiYXIifQ==.20kGGJaYekGTRFf8b0TwhuETcR8lv5z2363X5jf7G1yTWVTwOmte5Ii8L8_OQbYwPoiVHmZY6iJPbt_DhCN42AeFY74BcsUhR-BVrYUVhKK0RppuzEcSlILDNeQsJDLEL035CPm1VO6Jrgk7enQPIctVxUesRgswP71OpGvJxy3j1k_J8p0WzZvRZTe1D_2Misa0UDGwnEIHhmr97fIpMSZjFxlcygQw8QN34IHLHIXMaTY1eiCf4CCr6rOS9wUeu7P3CPkmFq9XhxBT_LLCmIMhHnxP5x27FUJE_JZlfek0MmARcrhpsZS2sFhHAiWrjxjOE27jkDtv1nEwn65wMw==",
+		defaultKeyFunc,
+		jwt.MapClaims{"foo": "paddedbar"},
+		true,
+		0,
+		nil,
+		jwt.SigningMethodRS256,
+	},
 	{
 		"basic expired",
 		"", // autogen

token.go

@@ -104,17 +104,17 @@ func ParseWithClaims(tokenString string, claims Claims, keyFunc Keyfunc, options
 // Deprecated: In a future release, we will demote this function to a non-exported function, since it
 // should only be used internally
 func EncodeSegment(seg []byte) string {
-	return strings.TrimRight(base64.RawURLEncoding.EncodeToString(seg), "=")
+	return base64.RawURLEncoding.EncodeToString(seg)
 }
 
 // DecodeSegment decodes a JWT specific base64url encoding with padding stripped
 //
 // Deprecated: In a future release, we will demote this function to a non-exported function, since it
 // should only be used internally
 func DecodeSegment(seg string) ([]byte, error) {
-	if l := len(seg) % 4; l > 0 {
-		seg += strings.Repeat("=", 4-l)
+	if strings.Contains(seg, "=") {
+		return base64.URLEncoding.DecodeString(seg)
 	}
 
-	return base64.URLEncoding.DecodeString(seg)
+	return base64.RawURLEncoding.DecodeString(seg)
 }