Struggling to use with waitgroup + context

[fugkco]

Hi!

I dunno what I'm doing wrong, but I'm trying to incorporate a waitgroup and a cancellable context, and I'm struggling to get anything out of this. The code below isn't producing the exact same thing, but I'm struggling to extract my code.

package main

import (
	"context"
	"github.com/nxadm/tail"
	"io"
	"log"
	"os"
	"sync"
	"time"
)

func main() {
	var wg sync.WaitGroup

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	tailFile(ctx, &wg, "/tmp/testing", os.Stdout)

	wg.Wait()
}

func tailFile(ctx context.Context, wg *sync.WaitGroup, path string, dest io.Writer) {
	realTailer, err := tail.TailFile(path, tail.Config{Follow: true, ReOpen: true})
	if err != nil {
		panic(err)
	}
	defer realTailer.Cleanup()

	wg.Add(1)
	go func() {
		defer wg.Done()
		for {
			select {
			case <-ctx.Done():
				log.Println("tail stopped")
				return
			case line := <-realTailer.Lines:
				switch {
				case realTailer.Err() != nil:
					log.Printf("tail err=%s", realTailer.Err())
					continue
				case line == nil:
					log.Println("tail = nil???")
					continue
				}

				if _, err := dest.Write([]byte(line.Text)); err != nil {
					log.Printf("write err=%s", err)
				}
			}
		}
	}()
}

For some reason, the code above for me seems to go into the line == nil branch and I'm struggling to figure out why. Any thoughts on what I could be doing wrong here?