Contains a low-level primitives for LN. Mostly it is for internal usage but some are useful for consumer's point of view. (e.g. LNMoney to represent milli-satoshis value)
Contains items for wire-protocol. FeatureBits, TLV, and P2P messages.
Contains modules and types for working with Cryptographic operations. For example LN-onion network encoding, aezeed for seed backups.
A module for creating LN-specific transactions. Mostly for internal usage.
Handles handshake and encryption against other peers.
Handles channel state. This module is pretty much WIP (not sure when it will be finished, as this is the most complex part in the LN protocol).
Contains primitives for Payment-related operations. The most important class is PaymentRequest,
a.k.a. bolt11-invoice, LN-invoice.
It also contains primitives for LSAT, the LN based http authentication mechanism. See here for PoC of AspNetCore middleware for LSAT.
Module for calculating payment routes. (WIP)