Work:

set foldlevelstart=99

Not Work:

set foldmethod=syntax

set nofoldenable

Use za zo zi to fold code.

Reference:

• https://vi.stackexchange.com/questions/12334/how-to-prevent-folding-when-vim-is-launched
• https://unix.stackexchange.com/questions/141097/how-to-enable-and-use-code-folding-in-vim