"Hagrid," said Harry, panting a bit as he ran to keep up, "did you say there are dragons at Gringotts?"
"Well, so they say," said Hagrid. "Crikey, I'd like a dragon."
"You'd like one?"
"Wanted one ever since I was a kid –– here we go."
They had reached the station. There was a train to London in five minutes' time. Hagrid, who didn't understand "Muggle money," as he called it, gave the bills to Harry so he could buy their tickets.
(Harry Potter and the Sorcerer's Stone)
Does the phrase mean ‘let’s go’ or ‘said when something bad starts happening again’?
(I guess the latter is more likely that Hagrid seems to blame himself.)
Best Answer
If you give someone something you can say "Here you go" to the person you are giving it to.
If I was bringing someone to the train station for example, I might say "here you go" on arriving at the station. I have given them the train station.
If I was bringing someone to the train station and I was also going to be travelling with them on the train, I might then say "here we go" on arriving at the station. I have given us the train station. This is the meaning of the sentence you mention above.
I would say "Here we go again" if someone started doing something again and again and that something was annoying me.