p1 := new(int)
fmt.Printf("p1 --> %#v \n ", p1) //(*int)(0xc42000e250) 
fmt.Printf("p1 point to --> %#v \n ", *p1) //0
var p2 *int
i := 0
p2 = &i
fmt.Printf("p2 --> %#v \n ", p2) //(*int)(0xc42000e278) 
fmt.Printf("p2 point to --> %#v \n ", *p2) //0

var s1 []int
if s1 == nil {
 fmt.Printf("s1 is nil --> %#v \n ", s1) // []int(nil)
}
s2 := make([]int, 3)
if s2 == nil {
 fmt.Printf("s2 is nil --> %#v \n ", s2)
} else {
 fmt.Printf("s2 is not nill --> %#v \n ", s2)// []int{0, 0, 0}
}

var m1 map[int]string
if m1 == nil {
 fmt.Printf("m1 is nil --> %#v \n ", m1) //map[int]string(nil)
}
m2 := make(map[int]string)
if m2 == nil {
 fmt.Printf("m2 is nil --> %#v \n ", m2)
} else {
 fmt.Printf("m2 is not nill --> %#v \n ", m2) map[int]string{} 
}
var c1 chan string
if c1 == nil {
 fmt.Printf("c1 is nil --> %#v \n ", c1) //(chan string)(nil)
}
c2 := make(chan string)
if c2 == nil {
 fmt.Printf("c2 is nil --> %#v \n ", c2)
} else {
 fmt.Printf("c2 is not nill --> %#v \n ", c2)//(chan string)(0xc420016120)
}

func modifySlice(s []int) {
 s[0] = 1
}
s2 := make([]int, 3)
fmt.Printf("%#v", s2) //[]int{0, 0, 0}
modifySlice(s2)
fmt.Printf("%#v", s2) //[]int{1, 0, 0}

func modifyMap(m map[int]string) {
 m[0] = "string"
}
func modifyChan(c chan string) {
 c <- "string"
}
m2 := make(map[int]string)
if m2 == nil {
 fmt.Printf("m2 is nil --> %#v \n ", m2) 
} else {
 fmt.Printf("m2 is not nill --> %#v \n ", m2) //map[int]string{}
}
modifyMap(m2)
fmt.Printf("m2 is not nill --> %#v \n ", m2) // map[int]string{0:"string"}
c2 := make(chan string)
if c2 == nil {
 fmt.Printf("c2 is nil --> %#v \n ", c2)
} else {
 fmt.Printf("c2 is not nill --> %#v \n ", c2)
}
go modifyChan(c2)
fmt.Printf("c2 is not nill --> %#v ", <-c2) //"string"

type Foo struct {
 name string
 age int
}
var foo1 Foo
fmt.Printf("foo1 --> %#v\n ", foo1) //main.Foo{age:0, name:""}
foo1.age = 1
fmt.Println(foo1.age)
foo2 := Foo{}
fmt.Printf("foo2 --> %#v\n ", foo2) //main.Foo{age:0, name:""}
foo2.age = 2
fmt.Println(foo2.age)
foo3 := &Foo{}
fmt.Printf("foo3 --> %#v\n ", foo3) //&main.Foo{age:0, name:""}
foo3.age = 3
fmt.Println(foo3.age)
foo4 := new(Foo)
fmt.Printf("foo4 --> %#v\n ", foo4) //&main.Foo{age:0, name:""}
foo4.age = 4
fmt.Println(foo4.age)
var foo5 *Foo = new(Foo)
fmt.Printf("foo5 --> %#v\n ", foo5) //&main.Foo{age:0, name:""}
foo5.age = 5
fmt.Println(foo5.age)