tour: Incorrect slicing behaviour on local AND remote gotour

[half-adder]

Context: http://127.0.0.1:3999/moretypes/10

given s := []int{2, 3, 5, 7, 11, 13}, s[1:4] gives [3 5 7]. This is correct. However, s[:4] gives [3 5 7 11] this is clearly incorrect. Here is the complete code:

package main

import "fmt"

func main() {
    s := []int{2, 3, 5, 7, 11, 13}

    s = s[1:4]
    fmt.Println(s)

    s = s[:4]
    fmt.Println(s)
}

and the output:

[3 5 7]
[3 5 7 11]

Program exited.

The same behavior is present at https://tour.golang.org/moretypes/10

[half-adder]

First statement mutates the slice object