hit Command+Shift+G from the Mac desktop (or Finder > Go > Go to Folder) and type in ~/Library to temporarily access the Library directory in the Finder.When you are done, close this window and it will no longer be visible.
I'm not sure if folders are hidden for Linux users.
find . -type d -name .arduino15
drwxrwxr-x 4 david david 4096 Dec 16 18:18 .arduino15