simple draft

Draft: create a bi-direction between a unix socket and a tcp socket.

Test:
Connect a tcp nc  to a unix socket echo server

```
go build gocat.go
go build unix_socket_server.go
```

```
./unix_socket_server
```

in another terminal 
```
./gocat
```

in another terminal

```
nc localhost 6666
<-hello world!
->hello world!
```