differences in copying pointers to a struct and modifying contents within it

pointerstructcopy.go

// https://play.golang.org/p/juDjWm9VC44
package main

import "fmt"

type T struct {
	Id   int
	Name string
	Flurb []string
}

func Copy(a *T, b *T) error {
	b.Id = 5
	b.Name = "gert"
	a = b
	return nil
}
func CopyThatActuallyCopies(a *T, b *T) error {
	b.Id = 5
	b.Name = "gert"
	*a = *b
	return nil
}

func main() {
	var a = &T{1, "one", []string{"dl"}}
	var b = &T{2, "two", []string{"bb"}}

	fmt.Println(a, b)
	Copy(a, b)
	fmt.Println(a, b)
	CopyThatActuallyCopies(a, b)
	fmt.Println(a, b)
  //pointers within the struct will get copied as pointers so they are all pointing to the same instance
	b.Flurb[0] = "asdf"
	fmt.Println(a, b)
  //modifying the slice itself makes it a new object so it is no longer pointing to the same instance as the one that was copied
	b.Flurb = append(b.Flurb, "blabla")
	fmt.Println(a, b)
	b.Flurb[0] = "0000"
	fmt.Println(a, b)
}