For those who have issue with openssl 1.1 and Ruby 2.3 via RVM on Mac Mojave, you could try following commands. The problem is Ruby 2.3 is not compatible with openssl 1.1
rvm pkg install openssl
PKG_CONFIG_PATH=$HOME/.rvm/usr/lib/pkgconfig rvm reinstall 2.3.3 --with-openssl-dir=$HOME/.rvm/usr