Update docs in jwt.go.

jwt/jwt.go

@@ -67,11 +67,15 @@ type Config struct {
 	// intended audience.
 	Audience string
 
+	// PrivateClaims optionally specifies custom private claims in the JWT.
 	// See http://tools.ietf.org/html/draft-jones-json-web-token-10#section-4.3
-	// PrivateClaims optionally specifies custome private claims in the JWT.
+	//
+	// Private claim values can be different types, therefore interface{} is
+	// used and marshalled using custom code.
 	PrivateClaims map[string]interface{}
 
-	// UseIDToken optionally uses ID token instead of access token.
+	// UseIDToken optionally uses ID token instead of access token when
+	// server returns both 'access_token' and 'id_token'.
 	UseIDToken bool
 }