close port in react code example

Example 1: how to close port 3000 running

### For Linux/Mac OS search (sudo) run this in the terminal:
$ lsof -i tcp:3000
$ kill -9 PID

### On Windows:
netstat -ano | findstr :3000
tskill typeyourPIDhere 

### change tskill for taskkill in git bash

Example 2: Port 3000 is already in use, but when I try to kill nothing is found

netstat -ano | findstr :3000
taskkill /PID "123" /F