Add defer to gopher Lua

[dukv2001]

• [ yes] GopherLua is a Lua5.1 implementation. You should be familiar with Lua programming language. Have you read Lua 5.1 reference manual carefully?
• [ yes] GopherLua is a Lua5.1 implementation. In Lua, to keep it simple, it is more important to remove functionalities rather than to add functionalities unlike other languages . If you are going to introduce some new cool functionalities into the GopherLua code base and the functionalities can be implemented by existing APIs, It should be implemented as a library.

Please answer the following before submitting your issue:

1. What version of GopherLua are you using? : 5.1
2. What version of Go are you using? : 1.15
3. What operating system and processor architecture are you using? :windows/x64
4. What did you do? :add lua defer
5. What did you expect to see? : defer in lua
6. What did you see instead? : no

function foo()
defer
print 'defer 1'
end

do
    defer print 'defer 2' end
end

defer print 'defer 3' end

print 'end'

end

https://github.com/peete-q/lua-defer

[rhettli]

yeah,i like this function,it is so cool.

[dukv2001]

In order to adapt to intelligent grammar tips, I think we should use the following grammar

defer(function()
print("call")
end)

Lua needs him so much

[rhettli]

In order to adapt to intelligent grammar tips, I think we should use the following grammar

defer(function()
print("call")
end)

Lua needs him so much

In order to adapt to intelligent grammar tips, I think we should use the following grammar

defer(function()
print("call")
end)

Lua needs him so much

yeah ,without defer , program may not close mysql handler when got an error:

[rhettli]

@dukv2001 but as you know , gopher-lua is build with go fully, without any other language code, maybe it is diffcat~ to put this function to it

[dukv2001]

No, it needs to be supported in the language. External functions can't

[aadog]

已经实现了这个功能，并且带智能提示