First Welcome!
What age is your new puppy? And congrats on adopting, you'll find a lot of people here have adopted dogs
Do you know his 'history'? Was he part of a litter born in a Shelter? Is he eating and drinking? Are his nature calls normal, i.e. firm but not hard stools, urinating properly no bad smell or discoloration? Have you changed his diet? Do you use a clicker for training? Has he got toys? Sorry for the 'inquisition' but the more information you can give us, the better we can help you
As your new puppy (what's his name please) has only been with you three days, he is still 'settling in' to his new home. If he came from a Shelter, he may not have had much, if any, play time or one on one time, so give him a few days to get used to his new surroundings. Even for a puppy not from a Shelter a new home is a MAJOR change in their little lives and they can take a few days to settle to their new surroundings.
Let him find his feet. Though three days is a bit long for a youngster, especially if he's just say, three months old.
If he continues to be too quiet and subdued, then I would take him for a vet check. Even if he's just had one at the Shelter, if that's appropriate. It's not normal, after a settling in period, for a young puppy to be very quiet and not run and play, even if they've come from a Shelter and not had any real playtime etc.. My youngest boy was a shelter/street kid, and he was up and playing within a matter of minutes after arriving home.
As my vet once said when I replied to his question as to how was my puppy with "driving me crazy
" -vet's reply "if he wasn't then you'd be worried and have something to worry about".
Also check out all the information on the Puppy Threads, there's a mass of really, good, sound, solid advice, from very experienced people. Starting from the very beginning Getting Your New Puppy etc.
Do keep us posted as to what is happening with your boy. And please, please, don't wait too long for a vet check if he is still continuing to remain quiet and not play. That's just not normal, ALL puppies have a play instinct and Goldens LOVE to play!