var-declared function's doc not generated

[book987]

Describe the bug
Currently function declared by var is ignored. But it indeed is a function, which might act as an API handler. The example below shows the case.

package main

func f() {}

// GetSth godoc
var GetSth = f

Furthermore, any variable pointing directly or indirectly to a function should not be ignored, and it's swag comment should be handled correctly.

package main

func f() {}

// F1 godoc
var F1 = f

// F2 godoc
var F2 = f1

// F3 godoc
var F3 = f2

To Reproduce
see above

Expected behavior
expect swag would generate docs realted to function declared by var

Screenshots
If applicable, add screenshots to help explain your problem.

Your swag version
e.g. 1.8.12

Your go version
e.g. 1.19

Desktop (please complete the following information):

• OS: mac
• Browser: firefox
• Version: [e.g. 22]

Additional context
no more context

[book987]

@ubogdan Hi, please take a look at this issue, if it is meaningful, there's a pr need review