Function bicoro::map_err

pub fn map_err<'a, I, O, A, E1, E2, F>(
    co: Coroutine<'a, I, O, Result<A, E1>>,
    f: F
) -> Coroutine<'a, I, O, Result<A, E2>>where
    F: FnOnce(E1) -> E2 + Send + 'a,

Convert E1 into E2

Sugar over bind