How can I setup file offset state with filebeat source code?

Elastic Stack Beats
1

I'm trying to import filebeat source code to read text from file. I understand that filebeat saves offset to filesystem so when it restarts, it won't read text from beginning of the file. How can I implement this function? I write a simple code below but everytime I restart the code, it reads the file from beginning.

package main

import (
	"fmt"
	"github.com/elastic/beats/filebeat/channel"
	"github.com/elastic/beats/filebeat/input"
	"github.com/elastic/beats/filebeat/input/file"
	"github.com/elastic/beats/filebeat/input/log"
	"github.com/elastic/beats/libbeat/beat"
	"github.com/elastic/beats/libbeat/common"
	"path"
	"sync"
	"time"
)

type eventCapturer struct {
	closed    bool
	c         chan struct{}
	closeOnce sync.Once
	events    chan beat.Event
}

func (o *eventCapturer) OnEvent(event beat.Event) bool {
	o.events <- event
	return true
}

func (o *eventCapturer) Close() error {
	o.closeOnce.Do(func() {
		o.closed = true
		close(o.c)
	})
	return nil
}

func (o *eventCapturer) Done() <-chan struct{} {
	return o.c
}

func NewEventCapturer(events chan beat.Event) channel.Outleter {
	return &eventCapturer{
		c:      make(chan struct{}),
		events: events,
	}
}

func main() {
	config, _ := common.NewConfigFrom(common.MapStr{
		"paths":     path.Join("/home/sf/logs", "*.log"),
		"close_eof": false,
	})
	events := make(chan beat.Event, 100)
	defer close(events)
	capturer := NewEventCapturer(events)
	connector := channel.ConnectorFunc(func(_ *common.Config, _ beat.ClientConfig) (channel.Outleter, error) {
		return channel.SubOutlet(capturer), nil
	})
	context := input.Context{
		Done:     make(chan struct{}),
		BeatDone: make(chan struct{}),
	}
	inp, err := log.NewInput(config, connector, context)
	if err != nil {
		fmt.Println(err)
		panic(err)
	}
	inp.Run()
	defer inp.Stop()

	timeout := time.After(30 * time.Second)
	done := make(chan struct{})
	for {
		select {
		case event := <- events:
			fmt.Println(event)
			if state, ok := event.Private.(file.State); ok && state.Finished {
				go func() {
					close(done)
					close(context.Done)
					close(context.BeatDone)
				}()
			}
		case <-done:
			return
		case <-timeout:
			fmt.Println("timeout waiting for closed state")
		}
	}
}

Sorry for my innocent question but is it legal to import filebeat like this?
Thanks.

2

Please help ...