Fake Time

Go faketime

Unfortunatelly, libfaketime not usable with golang. But we can write alternative for that.

libfaketime

When changing date, libfaketime amazing to do that.

In debian image

RUN apt-get update && apt-get install --no-install-recommends -y \
    libfaketime

After that just show that so file to LD_PRELOAD env and give the FAKETIME env to set the date.

LD_PRELOAD=/usr/lib/x86_64-linux-gnu/faketime/libfaketime.so.1 FAKETIME="2000-01-01 00:00:00" date

Default is seconds, FAKETIME="-120" is 2 minutes ago. But usable with "m", "h", "d" and "y" suffixes.

Use as start

export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/faketime/libfaketime.so.1

When we do that it is always show the same date. But if we add @ as prefix it will be start date.

export FAKETIME="@2000-01-01 00:00:00"

Now sub process run more than once date, than it will be increase the date.

/bin/bash -c 'while [ $SECONDS -lt 5 ]; do date; sleep 1; done'
# Sat Jan  1 00:00:00 UTC 2000
# Sat Jan  1 00:00:01 UTC 2000
# Sat Jan  1 00:00:02 UTC 2000
# Sat Jan  1 00:00:03 UTC 2000
# Sat Jan  1 00:00:04 UTC 2000