为什么可以使用指针或struct访问struct的成员呢？

package main

import (
    "fmt"
    "math"
)

type Vertex struct {
    X, Y float64
}

func (v Vertex) Scale(f float64) {
    v.X = v.X * f
    v.Y = v.Y * f
}

func (v Vertex) Abs() float64 {
    return math.Sqrt(v.X*v.X + v.Y*v.Y)
}

func main() {
    v := &Vertex{3, 4}
    fmt.Println(v.X)
    fmt.Println(v.Abs())
}

Here is my code: for v := &Vertex{3, 4}, v is a pointer which point to Vertex{3, 4}, but i find fmt.Println(v.X) is ok for v := Vertex{3, 4} or v := &Vertex{3, 4}, also for function func (v Vertex) Abs() float64 which is used for Vertex type, but using * Vertex type to call it is also ok.

what's the reason?