Line counter written in Go

main.go

package main

import (
    "bytes"
    "fmt"
    "io"
    "os"
)

func main() {
    args := os.Args[1:]

    if len(args) != 1 {
        fmt.Fprintln(os.Stderr, "Expected 1 argument: File path")
        os.Exit(1)
    }

    path := args[0]

    file, err := os.Open(path)

    if err != nil {
        fmt.Fprintf(os.Stderr, "Failed to open file: %v", err)
        os.Exit(1)
    }

    count, err := lineCounter(file)

    if err != nil {
        fmt.Fprintf(os.Stderr, "Encountered error while counting: %v", err)
        os.Exit(1)
    }

    fmt.Println(count)
}

func lineCounter(r io.Reader) (int, error) {
    buf := make([]byte, 32*1024)
    count := 0
    lineSep := []byte{'\n'}

    for {
        c, err := r.Read(buf)
        count += bytes.Count(buf[:c], lineSep)

        switch {
        case err == io.EOF:
            return count, nil

        case err != nil:
            return count, err
        }
    }
}