1.go

package main

import (
  "fmt"
)

type A struct {
	I int
}

func foo1(a A) A {
	return a
}

func foo2(a A) *A {
	return &a
}

func foo3(a *A) *A {
	return a
}

func foo4(a *A) A {
	return *a
}
func main() {
	a := A{1}
	b := foo1(a)
	c := foo2(a)
	d := foo3(&a)
	e := foo4(&a)
	a.I = 2
	fmt.Println("a.I", a.I, a)
	fmt.Println("b.I", b.I, b)
	fmt.Println("c.I", c.I, c)
	fmt.Println("d.I", d.I, d)
	fmt.Println("e.I", e.I, e)
}

gistfile1.txt

$ go run 1.go 
a.I 2 {2}
b.I 1 {1}
c.I 1 &{1}
d.I 2 &{2}
e.I 1 {1}