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: rawconn.go
    path of file: ./repos/sealer/vendor/github.com/marten-seemann/tcp
    
    the code of the file until where you have to start completion: // Copyright 2017 Mikio Hara. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package tcp

import (
	"errors"
	"net"
	"os"
	"runtime"
	"syscall"

	"github.com/mikioh/tcpopt"
)

// A Conn represents an end point that uses TCP connection.

    
func NewConn(c net.Conn) (*Conn, error) {
	type tcpConn interface {
		SyscallConn() (syscall.RawConn, error)
		SetLinger(int) error
	}
	var _ tcpConn = &net.TCPConn{}
	cc := &Conn{Conn: c}
	switch c := c.(type) {
	case tcpConn:
		var err error
		cc.c, err = c.SyscallConn()
		if err != nil {
			return nil, err
		}
		return cc, nil
	default:
		return nil, errors.New("unknown connection type")
	}
}