code: func (gl *gracefulListener) Accept() (c net.Conn, err error) {
  	c, err = gl.Listener.Accept()
  	if err != nil {
  		return
  	}
  	c = gracefulConn{Conn: c, connWg: gl.connWg}
  	gl.connWg.Add(1)
  	return
  }
docs: // Accept accepts a connection.