You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: epoll_linux.go
    path of file: ./repos/1m-go-tcp-server/2_epoll_server
    
    the code of the file until where you have to start completion: // +build linux

package main

import (
	"log"
	"net"
	"reflect"
	"sync"
	"syscall"

	"golang.org/x/sys/unix"
)

type epoll struct {
	fd          int
	connections map[int]net.Conn
	lock        *sync.RWMutex
}

func MkEpoll() (*epoll, error) {
	fd, err := unix.EpollCreate1(0)
	if e
    
func (e *epoll) Add(conn net.Conn) error {
	// Extract file descriptor associated with the connection
	fd := socketFD(conn)
	err := unix.EpollCtl(e.fd, syscall.EPOLL_CTL_ADD, fd, &unix.EpollEvent{Events: unix.POLLIN | unix.POLLHUP, Fd: int32(fd)})
	if err != nil {
		return err
	}
	e.lock.Lock()
	defer e.lock.Unlock()
	e.connections[fd] = conn
	if len(e.connections)%100 == 0 {
		log.Printf("total number of connections: %v", len(e.connections))
	}
	return nil
}