Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

1.9.2

Does this issue reproduce with the latest release?

I don't know.

What operating system and processor architecture are you using (go env)?

windows/amd64,

What did you do?

I was have a text file with size 6.79 GB. Then i read it with code :-

f, err := os.Open("filepath")
checkErr(err)
// get the file size
stat, err := f.Stat()
checkErr(err)
buf := make([]byte, stat.Size())
fmt.Println(stat.Size())
f.Read(buf)

Finally i need to write the buffer as a new file with this code :-

ioutil.WriteFile("temp.csv", []byte(buf), 0644)

What did you expect to see?

I expect the new written file will the same size as the file i was read which size is 6.79GB.

What did you see instead?

The new written file size was 2.79GB.