Explaining how nil in Go works for slices

slice.go

package main

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

func main() {
	var x []byte
	sliceHeader := *(*reflect.SliceHeader)(unsafe.Pointer(&x))
	fmt.Printf("SliceHeader (nil)          %#+v\n", sliceHeader)

	x = []byte{1, 2, 3}
	sliceHeader = *(*reflect.SliceHeader)(unsafe.Pointer(&x))
	fmt.Printf("SliceHeader (1, 2, 3)      %#+v\n", sliceHeader)

	x = make([]byte, 0)
	sliceHeader = *(*reflect.SliceHeader)(unsafe.Pointer(&x))
	fmt.Printf("SliceHeader (make([]byte)) %#+v\n", sliceHeader)

	x = append(x, 1)
	sliceHeader = *(*reflect.SliceHeader)(unsafe.Pointer(&x))
	fmt.Printf("SliceHeader (append)       %#+v\n", sliceHeader)
}