Mimic any binary
Just sprinkle on some code for logging stdin, let sit in prod for 2-3 weeks, and you have a really dumb keylogger.
Anything else:
$ mv ./ditto ./ls
$ ./ls
cmd go.mod ls pkg
Everything else:
$ ln -s ditto cat
$ ln -s ditto echo
$ ./echo Hello from ditto | ./cat -
Hello from ditto
$ ./ditto
go build cmd/ditto.go