The book of Jonah is an emotional roller coaster, and Jonah seems to be extremely volatile. He is not really the type of person that you would imagine being a preacher.
God told the prophet Jonah that He (God) was aware of what was going on in the world and that he had to go to Nineveh and warn them that they were fast approaching a time when God would judge them.
Initially, he disobeyed God and ran in the opposite direction. Then, after his near-drowning and rescue by a whale, he accepts the commission and sets off for Nineveh.
The story ends with his simmering anger with God for being forgiving. He thought that God should have damned the people of the sinful city of Nineveh. In his heart, Jonah obviously knew that God would forgive, which is why in chapter 4, verse 2, he says to God, 'This is what I was talking about in my country'. Presumably, he had argued with God before he decided to disobey, as he knew how God operated: if there was the slightest possibility that the people would turn from their sins, God would forgive them (and that really annoyed him). God is still the same today - He is 'long-suffering . . . not willing that any should perish but that all should come to repentance ', (a change of mind and faith in and obedience to God) 2 Peter 3:9.