Function connection_header_names 

pub fn connection_header_names(
    headers: &HeaderMap,
) -> impl Iterator<Item = HeaderName> + use<>

Available on crate features http and std only.

Return every syntactically valid field name nominated by Connection.

Invalid list members are ignored individually, so they cannot prevent a valid sibling nomination from being removed. The returned iterator owns a cheap snapshot of the Connection field values, so callers may mutate the source map while consuming it.