Examples don't work on my laptop

[oren]

Every example I try to run (except for mouse.cr) don't show anything. after a second or two the program terminates. no error is showing. echo $? return 0 so there is no error.

About my laptop:

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 16.04.6 LTS
Release:	16.04
Codename:	xenial

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$ uname -a
Linux oren 4.4.0-171-generic #200-Ubuntu SMP Tue Dec 3 11:04:55 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux