Rust所有权--与go对比学

如何拿返回值，如何不传递所有权就更改原值？如果想操作更改元变量要怎么做呢？

分别执行以下go代码：

func main() {
	var a = 10
	//calc1(a)
	//a = calc_return(a)
	calc2(&a)
	a = 100
	calc3(&a)

	fmt.Println(a)
}
func calc1(num int) {
	num += num
}
func calc_return(num int) int {
	num += num
	return num
}
func calc2(num *int) {
	*num += *num
}
func calc3(num *int) {
	*num += *num
}

rust代码：

use std::string;
fn main() {
    let mut s1  = String::from("learn rust");
    s1 =  foo_return(s1);
    println!{"{s1}"};  
    
}
fn  foo_return(s:String)->String{
    println!{"{s}"};
    s
}

use std::string;
fn main() {
    let mut s1  = String::from("learn rust");
    // foo1(s1);
    // foo2(&s1);
    foo3(&mut s1);
 
    println!{"{s1}"};
    foo3(&mut s1);
    
    
}
fn  foo1(s:String){
   
     println!{"{s}"};
}
fn  foo2(s:&String){
   
     println!{"{s}"};
}
fn  foo3(s:&mut String){
    s.push_str(",you can be 666");
     println!{"{s}"};
}

自己去体会其中的不同之处