.go

func (r *mutationResolver) UpdateUser(ctx context.Context, input UpdateUser) (User, error) {
   var fields = bson.M{}
   var user User

   update := false

   if input.First != nil && *input.First != "" {
      fields["first"] = *input.First
      update = true
   }
   if input.Last != nil && *input.Last != "" {
      fields["last"] = *input.Last
      update = true
   }
   if input.Email != nil && *input.Email != "" {
      fields["email"] = *input.Email
      update = true
   }

   if !update {
      return User{}, errors.New("no fields present for updating data")
   }

   err := r.users.UpdateId(bson.ObjectIdHex(input.ID), fields)
   if err != nil {
      return User{}, err
   }

   err = r.users.Find(bson.M{"_id": bson.ObjectIdHex(input.ID)}).One(&user)
   if err != nil {
      return User{}, err
   }

   user.ID = bson.ObjectId(user.ID).Hex()

   return user, nil
}