struct Foo {
pub mut:
    buf  shared []u8 = []u8{len: 20, init: 6}
    buf2 shared [20]u8
}

fn test_main() {
    mut foo := Foo{
        buf2: [20]u8{init: 5}
    }
    rlock foo.buf {
        if foo.buf.len > 0 {
            x := 10
            println('first ${x} bytes: ' + foo.buf[..x].str())
            sliced := foo.buf[..x]
            assert sliced == [u8(6), 6, 6, 6, 6, 6, 6, 6, 6, 6]
        } else {
            println('no data')
            assert false
        }
    }
    rlock foo.buf2 {
        x := 4
        println('first ${x} bytes: ' + foo.buf2[..x].str())
        assert foo.buf2[..x] == [u8(5), 5, 5, 5]
    }
}