Function handler_fn 

pub fn handler_fn<A, F, Fut>(f: F) -> ServiceFn<impl Fn(LambdaEvent<A>) -> Fut>
where
    F: Fn(A, Context) -> Fut,

👎Deprecated since 0.5.0: Use service_fn and LambdaEvent instead

Return a new ServiceFn with a closure that takes an event and context as separate arguments.