将切片附加到函数参数切片

我试图找出切片是如何工作的.请查看以下代码

package main

import "fmt"

type ByteSlice []byte

func (p *ByteSlice) Append(data []byte) {
    slice := *p
    *p = append(slice, data...)
}

func main() {
    var a ByteSlice
    a[0] = 3
    b := []byte{4,6,7}
    a.Append(b)
    fmt.Println(b)
}

正如您在append函数中看到的,我尝试将slice参数附加到调用中,但是我遇到以下错误:

panic: runtime error: index out of range

goroutine 16 [running]:
runtime.panic(0x4a14e0, 0x51333c)
    c:/go/src/pkg/runtime/panic.c:279 +0xe9
main.main()
    D:/Go/samples/src/method.go:16 +0x243

goroutine 17 [runnable]:
runtime.MHeap_Scavenger()
    c:/go/src/pkg/runtime/mheap.c:507
runtime.goexit()
    c:/go/src/pkg/runtime/proc.c:1445

goroutine 18 [runnable]:
bgsweep()
    c:/go/src/pkg/runtime/mgc0.c:1976
runtime.goexit()
    c:/go/src/pkg/runtime/proc.c:1445

goroutine 19 [runnable]:
runfinq()
    c:/go/src/pkg/runtime/mgc0.c:2606
runtime.goexit()
    c:/go/src/pkg/runtime/proc.c:1445
exit status 2

我错在哪里？