"It is you who have stood by me in my trials; and I confer a kingdom on you, just as my Father has conferred one on me, that you may eat and drink at my table in my kingdom; and you will sit on thrones judging the twelve tribes of Israel." 
Luke 22: 28-30

[Jesus] called his disciples to himself, and from them he chose Twelve, whom he also named apostles.
Luke 6: 13

The number of Apostles reflects the continuity of the Old and New Law and the fulfillment of the Old Covenant in the New Covenant established by Christ. It also looks ahead to the everlasting Kingdom of Heaven, where the faithful will be gathered under God's holy reign. In the Book of Revelation, “twelve apostles of the Lamb" have their names inscribed on the twelve foundations of the city, underscoring the Apostles' foundational role in the building of God's kingdom through their apostolic ministry. (Cf. CCC 865)

The number twelve appears in other parts of Scripture, each of which symbolizes a perfection of governance. In the Old Testament there were twelve patriarchs from Shem (the son of Noah) to Jacob, whom God renamed Israel. The sons and tribes of Israel, though there were thirteen, are in every instance recorded as a list of twelve names, usually but not always excluding Levi. There were twelve people anointed to serve governmental functions, including Aaron, Saul, David, and Solomon. In the New Testament the Book of Revelation presents twelve foundations of the heavenly Jerusalem, twelve gates, twelve pearls, and twelve angels, all of which symbolize the perfection of Heaven.

The Catechism of the Catholic Church, paragraph  763 addresses this question.

- The Didache Bible

All of the apostles except for Judas Iscariot spent the remainder of their lives preaching the Gospel.

According to Tradition, Saints Peter, Andrew, James, Philip, Bartholomew, Matthew, Thomas, James the son of Alphaeus, Simon the Zealot, and Judas Thaddeus were all martyred for the faith.

Saint John, the Apostle who remained with Jesus at the Crucifixion, was the only Apostle to die a natural death – and this in spite of attempts to kill him by boiling him in oil.

Judas Iscariot, after betraying Jesus, committed suicide (see Matthew 5 and Acts of the Apostles 1:18).

[Jesus said], "Amen, amen, I say to you, when you were younger, you used to dress yourself and go where you wanted; but when you grow old, you will stretch out your hands, and someone else will dress you and lead you where you do not want to go.”  He said this signifying by what kind of death he would glorify God. 

John 21:18-19