This is a very simple usage of a Go list to add hashed blocks and append a hash to each block that points to the hash of the previous block. You can use it to learn and visualize how a blockchain links the blocks and how a block can be set up to contain any kind of data we wish.
It's easier to think of a blockchain as blocks stacked on top of each other such as so:
|-----------------|
| index |
| data |
| time |
| SHA256 |
|-----------------|
^
/ \
|
|
|-----------------|
| index |
| data |
| time |
| SHA256 |
|-----------------|