Despite your child being shy it is still very important that they are able to build and maintain positive peer relationships in and out of school. Having a shy child should not mean loneliness and it should not be a barrier to making friends. What it does mean is that they mean need a helping hand from you.

Help them interact with small groups of children or just one at a time. Ask your child to invite some classmates to your house after school or at the weekend.
Introduce them to hobbies where they can make friends with children who enjoy the same activities. Any child will often find it easier to talk to someone when they are doing the same thing.
Suggest to their teacher that they work in a team rather than working alone.
Talk about who they are, who they could be friends with in their class, who do they like and who has shared interests?
Reassure your child that having friends is important but no-one needs more than a few close friends!
What have you done to help your child?