The SFTP protocol (and the golang sftp package) internally uses uint32 unix
time for expressing mtime. Hence it is a waste of memory to store it as 24-byte
time.Time data structure in long-lived data structures. So despite that the
golang sftp package uses time.Time as external interface, we can re-encode the
value back to the original format and save memory.
Co-authored-by: Tomasz Melcer <tomasz@melcer.pl>
