“Go ye into all the world, and preach the gospel to every creature” is a command, Christ’s command. Christ gave that command to all believers, not only to the Apostles. All those Apostles have died but believers are still alive to obey Christ’s commands.
1st Corinthians 15:1-4, “Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain. For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures.”
2nd Corinthians 5:10-11, “For we must all appear before the judgment seat of Christ; that every one may receive the things done in his body, according to that he hath done, whether it be good or bad. Knowing therefore the terror of the Lord, we persuade men...”
The command is to "Preach the gospel." The verb "preach" means to herald the message. It is the same word found in
2 Timothy 4:2--"Preach the Word."