var net.errInvalidInterfaceIndex

2 uses

	net (current package)
		interface.go#L22: 	errInvalidInterfaceIndex    = errors.New("invalid network interface index")
		interface.go#L131: 		return nil, &OpError{Op: "route", Net: "ip+net", Source: nil, Addr: nil, Err: errInvalidInterfaceIndex}