Fix issue with generating docs for embedded structures with alias instead of package name

[ShoshinNikita]

Issue

For example, there's a package github.com/user/repo/common which contains type Common:

package common

type Common struct {
    ID int `json:"id"
}

If we embed this type in another struct but use an alias instead of the real package name, swag will generate wrong documentation:

package main

import (
    c "github.com/user/repo/common"
)

type Response struct {
    c.Common
    Name string `json:"name"
} 

Generated documentation:

{
    "definitions": {
        "main.Response": {
            "type": "object",
            "properties": {
                "name": {
                    "type": "string"
                }
            }
        }
    }
}

Solution

We can suppose that pkgName is a package alias, if typeSpec is nil. So, we can just iterate through import aliases and check can we get non-nil typeSpec

[codecov-io]

Codecov Report

Merging #668 into master will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #668      +/-   ##
==========================================
+ Coverage   84.40%   84.45%   +0.04%     
==========================================
  Files           7        7              
  Lines        1866     1872       +6     
==========================================
+ Hits         1575     1581       +6     
  Misses        184      184              
  Partials      107      107              

Impacted Files	Coverage Δ
parser.go	80.38% <100.00%> (+0.11%)	⬆️

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[sdghchj]

It is also need to be considered that the embeded field here might be a alias type, for example:

type Common []string

Since a lot of work to do, I refactored a branch refactored.
@easonlin404 What's your idea?