// The new built-in function allocates memory. The first argument is a type,
// not a value, and the value returned is a pointer to a newly
// allocated zero value of that type.
func new(Type) *Type
new 开辟一块内存，用来存储Type类型的变量，返回指向该地址的指针。
Type可以为所有类型。
给变量赋值零值 zero value of that type。
一下是各个类型的零值：
bool -> false
numbers -> 0
string -> ""
struct -> 各自key的零值
pointers -> nil
slices -> nil
maps -> nil
channels -> nil
functions -> nil
interfaces -> nil
有些类型的零值是nil，这个又是什么鬼，可以参考阅读 https://blog.csdn.net/raoxiaoya/article/details/108705176
值为nil的变量是没法操作的。
p := new([]int)
fmt.Println(*p == nil) // true
fmt.Printf("%p\n", p) // 0xc0000044a0
fmt.Println(*p) // []
(*p)[0] = 1 // panic: runtime error: index out of range [0] with length 0
p := new([]int)var p *[]intnew 常用在需要生成零值的结构体指针变量
p := new(Per)
等价于
p := &Per{}
接下来看一看make
// The make built-in function allocates and initializes an object of type
// slice, map, or chan (only). Like new, the first argument is a type, not a
// value. Unlike new, make's return type is the same as the type of its
// argument, not a pointer to it. The specification of the result depends on
// the type:
// Slice: The size specifies the length. The capacity of the slice is
// equal to its length. A second integer argument may be provided to
// specify a different capacity; it must be no smaller than the
// length. For example, make([]int, 0, 10) allocates an underlying array
// of size 10 and returns a slice of length 0 and capacity 10 that is
// backed by this underlying array.
//
// Map: An empty map is allocated with enough space to hold the
// specified number of elements. The size may be omitted, in which case
// a small starting size is allocated.
//
// Channel: The channel's buffer is initialized with the specified
// buffer capacity. If zero, or the size is omitted, the channel is
// unbuffered.
func make(t Type, size ...IntegerType) Type
make 开辟一块内存，用来存储Type类型的变量，返回此变量。
Type只能是 slice, map, chan。
初始化类型的值 initializes an object of type。因为它们三个的零值是nil，没法使用，因此还需要进一步赋予合理的值，叫做初始化。
a := make([]int, 1, 10)
b := make(map[string]string)
c := make(chan int, 1)