This program is similar to program uptime.
But mine shows when computer powers up.
Of course I can use uptime -s to know this, but then it shows only when computer powers up without showing other parameters.
And I wrote simple program in Go.
~$ go get github.com/janczer/uptime
~$
~$ uptime
~$ 21:33:40 up 0:58, power on 20:34:48, load average: 0.68, 1.52, 1.34