Gotta, Wanna, Gonna, are used in written English to represent the words when they are pronounced > informally. They are not slang.
gotta = got to
wanna =want to
Here in Ontario Canada , I can report that everyone I know, even highly educated people, use these forms normally. People in business meetings, professors giving lectures,... everyone. Sometimes people are being slow, clear, and deliberate, in which case they will pronounce the full phrase, which does sound more formal by comparison.
Me? I don't remember when was the last time I spoke: I am going to ... ...
Ain't 是个百搭字=am not, are not, is not, have not, have no
Ain't no sunshine 歌词: 为了rhym也是拼了啊, 什么语法不语法都是爆弱了,
Ain't no sunshine= there is no sunshine,
“It goes with everything."