golang. Can you suggest what is the problem?

Question

go

Error: invalid operation: post["attachments"] (type interface {} does not support indexing)

posts := wall["response"].(map[string]interface{})["items"].([]interface{})
  for _, post := range posts {
    attachments := post["attachments"].([]interface{})

    for _, attachment := range attachments {

Answer 1

Captain obviously states that: post["attachments"] (the interface {} type does not support indexing).

Answer 2

It turns out posts has type []interface{}. Accordingly, post is of type interface{}, not map[string].