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You're right. But it will return something: https://go.dev/play/p/Cz6aeGpURgo

  my_map := make(map[int32][]int64)
  val := my_map[123]
  val = append(val, 456)
  my_map[123] = val
  fmt.Println(my_map)
prints `map[123:[456]]`

I guess it's convenient compared to Rust's strict approach with entry API. But also, what I found is that golang's subscript returns nil in one case: if the value type is a nested map.

  my_map := make(map[int32]map[int32]int64)
  val := my_map[123]
  val[456] = 789
  my_map[123] = val
  fmt.Println(my_map)
output:

  panic: assignment to entry in nil map


You can test for existence:

    val, ok := my_map[123]
    if ok {
        ...
    }
https://go.dev/blog/maps#working-with-maps


It returns the zero value for all types, including arrays (which is nil).

nil is equivalent to the empty array, which is why the rest of the code works as it does.




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