import { BufReader } from "https://deno.land/std@0.223.0/io/mod.ts";
peek()
returns the next n
bytes without advancing the reader. The
bytes stop being valid at the next read call.
When the end of the underlying stream is reached, but there are unread
bytes left in the buffer, those bytes are returned. If there are no bytes
left in the buffer, it returns null
.
If an error is encountered before n
bytes are available, peek()
throws
an error with the partial
property set to a slice of the buffer that
contains the bytes that were available before the error occurred.