Golang - Arduino communication via Serial

main.go

package main

import (
	"log"
	"github.com/tarm/serial"
	"bufio"
	"fmt"
)

func main() {
	c := &serial.Config{Name: "COM3", Baud: 9600}
	s, err := serial.OpenPort(c)
	if err != nil {
		log.Fatal("Cannot open port. ", err)
	}

  _, err = s.Write([]byte(`{"name":"someName","data":[null,false,1,"str",{"key1":"val"1}]}`))
	if err != nil {
		log.Fatal("Cannot write bytes. ", err)
	}

	scanner := bufio.NewScanner(s)
	for scanner.Scan() {
		fmt.Println("======>", scanner.Text())
	}

	if scanner.Err() != nil {
		log.Fatal(err)
	}
}

sketch.ino

char rx_byte;

String stringOne = String('\0');

void setup() {
  // initialize serial:
  Serial.begin(9600);
}

void loop() {
  // if there's any serial available, read it:
  if (Serial.available() > 0) {
    rx_byte = Serial.read();
        
    Serial.print("=====> ");
    Serial.println((int)rx_byte);
    
    if (rx_byte == EOF || rx_byte == '\r' || rx_byte == '\n') {
      Serial.print("you typed: ");
      Serial.println(stringOne);

      Serial.print("len: ");
      Serial.println(stringOne.length());
      
      stringOne = String('\0');
    } else {
      stringOne.concat(rx_byte);
    }

  }
}

bufio.Scanner: token too long