in the story julius caesar , was antony a good friend to caesar ?

There are many shades of grey in terms of Antony's relationship with Caesar.

"Antony is a friend of Caesar. Antony claims allegiance to Brutus and the conspirators after Caesar's death in order to save his own life. Later, however, when speaking a funeral oration over Caesar's body, he spectacularly persuades the audience to withdraw its support of Brutus and instead condemn him as a traitor. With tears on his cheeks and Caesar's will in his hand, Antony engages masterful rhetoric to stir the crowd to revolt against the conspirators. Antony's desire to exclude Lepidus from the power that Antony and Octavius intend to share hints at his own ambitious nature."

I suppose, like most of us, Antony looks after himself. He seeks to remedy his guilt through the power of rhetoric, but Caesar is betrayed by him in the end.