How to do a asynchronous function inside a for loop

First I am searching the GroupMember model for all Groups the user is a member of. When they're found I get the result.

I want to loop through the result and get every group from the Group model. But how can I do an asynchronous function inside a for / forEach and go to the next iteration only when the asynchronous function is finished?

Because right now the groups array will get the first iteration over and over.

GroupMember.findAll({
    Where : {
      userID : userID
    }
  })
  .then(function(result) {
    var groups = []
    var itemsProcessed = 0;

    result.forEach(function(listItem, index, array) {
      var groupID = listItem.dataValues.groupID;

      Group.find({
        Where : {
          groupID: groupID
        }
      })
      .then(function(group) {

        groups.push(group.dataValues);
        itemsProcessed++;
        if(itemsProcessed === array.length) {

          done(null, groups);
        }
      });
    })

  })
  .catch(function(error) {
    done(error);
  });

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