how to add multiple white list in MySQL 5.7

Now I want to add multiple white list in MySQL 5.7, I know how to add one and range white list like this:

GRANT ALL PRIVILEGES ON mydb.* TO 'username'@'10.20.%';

and if I want to add multiple whitle list in one user(range1,range2,range……):

GRANT ALL PRIVILEGES ON mydb.* TO 'username'@'10.20.%';
GRANT ALL PRIVILEGES ON mydb.* TO 'username'@'192.20.%';

what should I do?