Both of them are correct.
I voted for either because both of them can be used as preposition to mean(( at some period of time)).
i confuse between in and during but i voit during i think its the best ansowr
It depends on speaker's condition.
If the speaker worked all the summer, the answer is "during".
If the speaker worked several hours or days, we use "in".
How about this?
I worked there all summer long!
Its sound is very emphasis!
During= period of time.