I want to step through the door full of curiosity, wondering: what is it going to be like, that cottage of darkness?
Finally we find out what happens when death comes: our speaker wants die with a sense of curiosity, open to what might happen in death, or after it. She gives death an image: a cottage of darkness.
It doesn't sound too strange to want to meet death without a lot of fear, but our speaker take it a step further. She wants to go with her eyes open (so to speak) and see what there is to see.
By giving death a place – a cottage – she's playing with our ideas of death. Normally we think it's an event, or an ending. But she gives it a location (and not a conventional one like heaven or hell), which suggests we go on existing.
For our speaker, death isn't an end, it's a transition – like walking through a door and into a cottage. That doesn't sound so scary. Cottages are usually comfy, homey places. It's not like walking into a castle or dungeon.
The darkness could also signify the unknown.
For our speaker, though, the unknown doesn't seem to be a source of terror. Actually the opposite: a source of wonder and possibility.