cannot infer an appropriate lifetime for lifetime parameter '_ in function call due to conflicting requirements

i have a vector of a struct

 let list = vec![
        ListenerList {
            listener: Pattern {
                cmd: "sum"
            },
            handler: |listener, connection| Box::pin(simple_handler(listener, connection))
        }
    ];

here is my struct

pub struct ListenerList<'a>{
    pub listener: Pattern<'a>,
    pub handler: fn(Subscription, &Connection) -> Pin<Box<dyn futures::Future<Output = ()>>>
}

and here is my simple_handler function

async fn simple_handler(listener: Subscription, connection: &Connection){
    println!("work?")
}

when i compile it i get this error

error[E0495]: cannot infer an appropriate lifetime for lifetime parameter '_ in function call due to conflicting requirements
  --> src/main.rs:19:54
   |
19 |             handler: |listener, connection| Box::pin(simple_handler(listener, connection))
   |                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |

>Solution :

The problem is in the definition of the handler field of ListenerList, which has this type:

fn(Subscription, &Connection) -> Pin<Box<dyn futures::Future<Output = ()>>>

Due to Rust’s default trait object lifetime rules, it desugars to the trait object getting a 'static bound, which we don’t want:

fn(Subscription, &Connection) -> Pin<Box<dyn futures::Future<Output = ()> + 'static>>

To fix this, specify the lifetime as '_:

fn(Subscription, &Connection) -> Pin<Box<dyn futures::Future<Output = ()> + '_>>