Mapping stateful fields

[antegral]

Problem

The following code to map proto to discordgo struct:

return &discordgo.Channel{
	ID:                   buf.Id,
	GuildID:              buf.GuildId,
	Name:                 buf.Name,
	Topic:                buf.Topic,
	Type:                 discordgo.ChannelType(buf.Type),
	LastMessageID:        buf.LastMessageId,
	LastPinTimestamp:     util.PbTimestamp2AsTimePtr(buf.LastPinTimestamp),
	MessageCount:         int(buf.MessageCount),
	MemberCount:          int(buf.MemberCount),
	NSFW:                 buf.Nsfw,
	Icon:                 buf.Icon,
	Position:             int(buf.Position),
	Bitrate:              int(buf.Bitrate),
	Recipients:           recipients,
	Messages:             nil, // Getting Library Internal State
	PermissionOverwrites: permissionOverwrites,
	UserLimit:            int(buf.UserLimit),
	ParentID:             buf.ParentId,
	RateLimitPerUser:     int(buf.RateLimitPerUser),
	OwnerID:              buf.OwnerId,
	ApplicationID:        buf.ApplicationId,
	ThreadMetadata: &discordgo.ThreadMetadata{
		Archived:            buf.ThreadMetadata.Archived,
		AutoArchiveDuration: int(buf.ThreadMetadata.AutoArchiveDuration),
		ArchiveTimestamp:    buf.ThreadMetadata.ArchiveTimestamp.AsTime(),
		Locked:              buf.ThreadMetadata.Locked,
		Invitable:           buf.ThreadMetadata.Invitable,
	},
	Member: &discordgo.ThreadMember{
		ID:            buf.Member.Id,
		UserID:        buf.Member.UserId,
		JoinTimestamp: buf.Member.JoinTimestamp.AsTime(),
		Flags:         int(buf.Member.Flags),
		Member:        BufMemberToStruct(buf.Member.Member),
	},
	Members:       nil, // Getting Library Internal State
	Flags:         discordgo.ChannelFlags(buf.Flags),
	AvailableTags: availableTags,
	AppliedTags:   buf.AppliedTags,
	DefaultReactionEmoji: discordgo.ForumDefaultReaction{
		EmojiID:   buf.DefaultReactionEmoji.EmojiId,
		EmojiName: buf.DefaultReactionEmoji.EmojiName,
	},
	DefaultThreadRateLimitPerUser: int(buf.DefaultThreadRateLimitPerUser),
	DefaultSortOrder:              defaultSortOrder,
	DefaultForumLayout:            discordgo.ForumLayout(buf.DefaultForumLayout),
}

In the struct above, Messages and Members are stored in the discordgo library's internal stateful storage,
and it's inappropriate to send all the data on every request.