If you need darkness to sleep, then you need to bring your sleeping mask to bed in Norway because it does not get completely dark during the summer months in Norway. In the northern Norway we even have midnight sun.
The summer hike photos in this article is taken around 11 pm at June 9th 2018. Yes, close to midnight. As you can see, the sun is still up on the sky.
A couple years ago I was in Bodo, in northern Norway. When I was looking out of the hotel window at midnight, I could not see if it was day or night. Of course you know if it is day or night by looking at your watch or keeping track of the day routines.
Buying sleeping mask in Norway
You can also buy a sleeping mask in Norway. I guess many hotels sell them, you can buy them at most airports in Norway too.
If you are in a larger city in Norway then you can look for shops as “Clas Ohlson”, just like Home Depot stores, selling sleeping masks for around €5 or 5 USD.