UART (serial) communication speed with raspberry pi is very slow

[mjk14]

Hi. I use a raspberry pi 4 UART port for communication but we should 2s delay in r/w data on it for correctly working. this speed is very slow for my scenario. how can I solve it?
library version: serialPort ^9.2.8
raspberry pi version: 4 B
bouadrate: 115200
OS: ubuntu 20.04
nodejs version:14.18.2
my code:(uart.js)

const serialport=require('serialport');
let port=new serialport("/dev/ttyS0",{baudRate:115200,autoOpen: true},(err)=>{
if(err)
return console.log('serial port connection failed => '+err);
});

async function delay(n) {
return new Promise(done => {
setTimeout(() => {
done();
}, n);
});
}

async function writeToSerial(){
while(1){
port.write("hi serialport", function(err) {
if (err) {
return console.log('Error on write: ', err.message)
}
})
await delay(2000);
}
}
writeToSerial();

const Readline=serialport.parsers.Readline;
const parser=new Readline();
port.pipe(parser);

//read data from serial port
parser.on('data',(message)=>{
console.log(message.toString());
});