Nodejs ERR_HTTP_HEADERS_SENT Cannot set headers after they are sent to the client

Question

I'm having the following problem:

node:_http_outgoing:576
    throw new ERR_HTTP_HEADERS_SENT('set');
    ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at new NodeError (node:internal/errors:371:5)
    at ServerResponse.setHeader (node:_http_outgoing:576:11)
...

I had a look here and here:

But I couldn't solve it, can you help me?

Code:

const express = require("express");
const app = express();
const port = 3001;

const { spawn } = require('node:child_process');
const ls = spawn('adb', ['logcat']);

app.get("/", (req, res) => {
  res.setHeader('Content-Type', 'application/json');

  let json = {}

  ls.stdout.on('data', (data) => {
    const [date, time, pid, pid2, priority, ...other] = String(data).replace(/\s+/g, ' ').split(" ");
    json = {
      date,
      time,
      pid: `${pid}-${pid2}`,
      priority,
      other: other.filter(Boolean)
    }

    console.log("---S");
    console.log(`${data}`);
    console.log(json);
    console.log("---E\n");

    res.json(json);
  });
  
  ls.stderr.on('data', (data) => {
    console.error(`stderr: ${data}`);
  });
  
  ls.on('close', (code) => {
    console.log(`child process exited with code ${code}`);
  });

  res.json(json);
});

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});