Whats wrong with the below code

I'm very new to rust and recently I came across reference lifetime .I was learning this topic and wrote below code. Here I'm trying to have a reference to 'Bar' in 'Foo' struct.

struct Foo<'a>{
    a:i32,b:i32,bar:&'a Bar,

struct Bar{

impl Foo<'a>{
    fn setup<'a>(&mut self) {
        println!("{} {} {:?}",self.a,self.b,self.bar);

fn main() {
    let bar = Bar{s:String::from("hello\n")};

getting below error when i compile the code

   Compiling playground v0.0.1 (/playground)
error[E0261]: use of undeclared lifetime name `'a`
  --> src/main.rs:12:10
12 | impl Foo<'a>{
   |     -    ^^ undeclared lifetime
   |     |
   |     help: consider introducing lifetime `'a` here: `<'a>`

For more information about this error, try `rustc --explain E0261`.
error: could not compile `playground` due to previous error

What's the correct way of having a reference inside a struct which also has impl block

You need to do the following:

- impl Foo<'a>
+ impl<'a> Foo<'a>
    (Need to declare lifetime here)

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