Revert "Merge branch 'master' of https://github.com/sczy/first_demo"

This reverts commit e65b8d08db52b2505fc1bf976ad28c23bed82600, reversing
changes made to 506f4f78cb978023f84315a6c059f26134a11688.
Revert 0d93b8b..c94805e

This rolls back to commit 0d93b8b270afbe6fa1cde4c96ea2d646da11a37a.