Paul says in 2 Timothy 4 that the time of his departure was at hand.  The image is of a ship being unmoored and the ropes cast off so that it can set sail.  Paul knows that he is about to die.

At the end of his Christian course he knew of no other name, no other way, than Jesus, who had called him out of darkness to His marvelous light. He had not preached to others and himself become a castaway. He had kept the faith.. In the moment of death not that is the all-important factor that he has carefully preserved the true doctrine and defended it against all error and errorists. Every Christian, every pastor, must do that. That is God’s will and command. Yet the all-important thing in the hour of death is personal faith. This personal faith alone, which united him with Jesus, enabled Paul to fight the good fight, to finish his course. There can be no reasonable doubt that he had this personal faith in mind when he penned these majestic words of triumph and victory. “Henceforth there is laid up for me a crown of righteousness,” Theodore Laetsch