avoid name break in chatgpt.SendMessage

[yuldashboev]

because there is no logic below for loop, we can just return from the function making code clearer.

[yuldashboev]

Consider the code below causing data racing because of unprotected conversations map

```

chgpt := chatgpt.Init()

go func() {
	ch, err := chgpt.SendMessage("test-racing", 123456)
	if err != nil {
		panic(err)
	}

	for range ch {
	}
}()

go func() {
	ch, err := chgpt.SendMessage("test-racing", 123457)
	if err != nil {
		panic(err)
	}

	for range ch {
	}
}()

Fixed this data racing by protecting map with mutex.