This coming Sunday, with the celebration of the Feast of Pentecost, marks the end of the Easter Season. And for that reason, for the Mass for Pentecost it is indicated in the Missal that the dismissal should have the beautiful (when sung) double-alleluia.
Here it is in Latin with chant notation:
Here it is sung in Latin, in St. Peter’s Basilica:
In English there are various options, one being —
Go in peace, alleluia, alleluia.
— sung to the same tune.
This short and simple chant is one of the most beautiful of the entire year! I hope that they will remember to use it in your parish and that it will be sung!