How switch works?

Question

go

test1 := false
  test2 := true
  test3 := false

  switch {
  case test1:
    fmt.Println(1)
    fallthrough
  case test2:
    fmt.Println(2)

    fallthrough

  case test3:
    fmt.Println(3)
  }

Outputs 2.3. Why?

Answer 1

This is described in the specification for the goshka.
That is, fallthrough transfers control to the first line of the next case without checking any conditions.