Go code to stream file to client which hasn't completed

streamFile.go

package main

import (
	"net/http"
	"os"
	"time"
)

// function to generate file in 10 seconds
func generateFile(done chan bool) {
	f, _ := os.OpenFile("example.txt", os.O_TRUNC|os.O_CREATE|os.O_WRONLY, 0644)
	defer f.Close()

	for i := 0; i < 10; i++ {
		f.WriteString(time.Now().String() + "\n")
		time.Sleep(1 * time.Second)
	}
	done <- true
}

func main() {
	os.Remove("example.txt")

	http.HandleFunc("/", downloadHandler)
	http.ListenAndServe(":8080", nil)
}

func downloadHandler(w http.ResponseWriter, r *http.Request) {
	// Set the appropriate headers for file download
	w.Header().Set("Content-Disposition", "attachment; filename=example.txt")
	w.Header().Set("Content-Type", "application/octet-stream")

	done := make(chan bool)
	lastByteRead := 0
	go generateFile(done)
	time.Sleep(1 * time.Second) // wait for file to be created

	f, _ := os.Open("example.txt")
	defer f.Close()

	for {
		select {
		case <-done:
			return
		default:
			// read file in chunks of 1024 bytes
			f.Seek(int64(lastByteRead), 0)
			buf := make([]byte, 1024)
			n, err := f.Read(buf)
			if err != nil && err.Error() == "EOF" {
				return
			}

			w.Write(buf[:n])
			w.(http.Flusher).Flush()
			lastByteRead += int(n)

			time.Sleep(1 * time.Second)

		}
	}

}