According to https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-PARAMKEYWORDS

If the host name starts with @, it is taken as a Unix-domain socket in the abstract namespace (currently supported on Linux and Windows).

However tokio-posgres connect prevents host=@... ; the error is

called Result::unwrap() on an Err value: Custom { kind: Uncategorized, error: "failed to lookup address information: Name or service not known" }

And the backtrace points to this line https://github.com/sfackler/rust-postgres/blob/02463b1/tokio-postgres/src/connect.rs#L98