How to check if there is any data left to read in a bufio.Reader in Go?

In Go, you can use the Peek() method of a bufio.Reader to check if there is any data left to read without consuming it.

Here's an example:

package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	// Create a new Reader from stdin
	reader := bufio.NewReader(os.Stdin)

	// Read a line of input
	line, err := reader.ReadString('\n')
	if err != nil {
		fmt.Println("Error reading input:", err)
		return
	}

	// Check if there is any remaining data
	remaining := reader.Buffered() > 0
	fmt.Println("Remaining data:", remaining)

	// Print the line
	fmt.Println("Read line:", line)
}

In this example, reader.Buffered() returns the number of bytes that can be read from the internal buffer without making additional I/O calls. By checking if this value is greater than 0, you can determine if there is any data left to read.

Note that Peek() method also returns the next n bytes without advancing the reader, so you can use it instead of Buffered() if you need to check the actual content of the remaining data.