go语言中string和[]byte互转遇到的奇怪问题？

先上代码：

package main

import (
    "fmt"
    "reflect"
    "unsafe"
)

func printAddr(format string, ptr interface{}) {
    p := reflect.ValueOf(ptr).Pointer()
    h := (*uintptr)(unsafe.Pointer(p))
    fmt.Printf(format, *h)
}

func tostring(bs []byte) string {
    return *(*string)(unsafe.Pointer(&bs))
}

func tobyte(s string) []byte {
    return *(*[]byte)(unsafe.Pointer(&s))
}

func main() {
    s := "hello,world!"
    b := tobyte(s)
    h := make([]byte, 30)
    h = b[0:2]
    d := tostring(h)

    printAddr("字符串的地址:%x\n", &s)
    printAddr("转换成[]byte的地址:%x\n", &b)
    printAddr("修改后的[]byte地址:%x\n", &h)
    printAddr("修改后[]byte转换成字符串的地址:%x\n", &d)

  // 这样可以正常输出
    fmt.Println(s, " b:", b, " h:", h, " d:", d)
    // 这样就报错
    //fmt.Println(s, " b:", b, " h:", h, " d:", d， s)
}

报错信息是：
panic: runtime error: slice bounds out of range

goroutine 1 [running]:
main.main()
D:/practice/src/studyGo/main.go:27 +0x47e

h := make([]byte, 30)
h = b[0:2]
    这两句有问题，正确的是
    h := b[0:2]
    或者
     var h []byte
h = b[0:2]