It's immediately clear a couple of points — square brackets are needed here, not curly ones. What do the three curly braces struct{}{} mean?

In Go, the expression struct{}{} creates an empty struct without fields. Three curly braces struct{}{}{} look like nested creation of an empty struct, but syntactically, this is incorrect.

If three curly braces appear in a row in the code, it might be a typo or an attempt to create a slice of empty structs, for example:

slice := []struct{}{{}, {}, {}}

Here, []struct{}{} is a slice of empty structs, and the curly braces inside create individual elements.

Thus, struct{}{} is an empty struct, and square brackets [] are used to create slices or arrays. It's important to distinguish these constructs to work correctly with types in Go.