When the TCP connection close in this code?

When I read this opensource code.

I have two questions about the two functions:

func listenTCP() {
    for {
        conn, err := tcpListener.Accept()
        if err != nil {
            if netErr, ok := err.(net.Error); ok && netErr.Temporary() {
                log.Printf("Temporary error while accepting connection: %s", netErr)
            }

            log.Fatalf("Unrecoverable error while accepting connection: %s", err)
            return
        }

        go handleTCPConn(conn)  // check below
    }
}


func handleTCPConn(conn net.Conn) {
    log.Printf("Accepting TCP connection from %s with destination of %s", conn.RemoteAddr().String(), conn.LocalAddr().String())
    defer conn.Close()
    
    remoteConn, err := conn.(*tproxy.Conn).DialOriginalDestination(false)
    if err != nil {
        log.Printf("Failed to connect to original destination [%s]: %s", conn.LocalAddr().String(), err)
        return
    } 
    defer remoteConn.Close()

    var streamWait sync.WaitGroup
    streamWait.Add(2)

    streamConn := func(dst io.Writer, src io.Reader) {
        io.Copy(dst, src)
        streamWait.Done()
    }

    go streamConn(remoteConn, conn)
    go streamConn(conn, remoteConn)

    streamWait.Wait()
}

Based on my understanding, I draw this diagram:

You see, the handleTCPConn created two goroutines for transmitting two direction(left -> right; right -> left)'s traffic,

My questions are:

1. You see the code use sync.WaitGroup, if they only send left-> right traffic, there is no traffic in opposite direction, so the handleTCPConn will not end, right? if it is, the listenTCP for loop will create many of those handleTCPConn function calls, is there nothing wrong with this program?

2. Every time the handleTCPConn is used, it will create a TCP connection to the remote server.

remoteConn, err := conn.(*tproxy.Conn).DialOriginalDestination(false)

My question is still in question 1, you can see that the handleTCPConn transmit the traffic once in both directions, and then ends it, whether the TCP connection is closed when does handleTCPConn end? if they only transmit part of the data of a file(as per the application layer view), whether it is closed too? (i mean, if A->B->C: part data , then C->B->A: ACK ) .