Function serde_skip::num_from_str_or_default

pub fn num_from_str_or_default<'de, T, D>(
    deserializer: D
) -> Result<T, D::Error> where
    D: Deserializer<'de>,
    T: FromStr + Deserialize<'de> + Default,
    <T as FromStr>::Err: Display, 

Use as

#[serde(deserialize_with = "num_from_str_or_default")]
pub number: u64,