use swaggertype tag to supported custom type

[lfaoro]

Describe the bug
Sometimes swag init panics out of the blue, other times generates without error.

To Reproduce

$ make doc
cd srv && swag init -g main.go && cd ..
2018/09/03 15:36:00 Generate swagger docs....
2018/09/03 15:36:00 Generate general API Info
panic: assignment to entry in nil map

goroutine 1 [running]:
github.com/swaggo/swag.(*Operation).ParseParamComment(0xc42045a120, 0xc42002a34a, 0x31, 0xc4204e2b00, 0x7, 0x39)
        /Users/lfaoro/go/src/github.com/swaggo/swag/operation.go:150 +0x83e
github.com/swaggo/swag.(*Operation).ParseComment(0xc42045a120, 0xc42002a340, 0x3b, 0xc4204e2b00, 0x0, 0x0)
        /Users/lfaoro/go/src/github.com/swaggo/swag/operation.go:69 +0x3b8
github.com/swaggo/swag.(*Parser).ParseRouterAPIInfo(0xc4204cc5c0, 0xc4204e2b00)
        /Users/lfaoro/go/src/github.com/swaggo/swag/parser.go:297 +0x17b
github.com/swaggo/swag.(*Parser).ParseAPI(0xc4204cc5c0, 0x14b1da9, 0x2, 0x7ffeefbff7bd, 0x7)
        /Users/lfaoro/go/src/github.com/swaggo/swag/parser.go:89 +0x218
github.com/swaggo/swag/gen.(*Gen).Build(0xc420177988, 0x14b1da9, 0x2, 0x7ffeefbff7bd, 0x7, 0x14b52cc, 0xe, 0x14b395b, 0x9, 0x0, ...)
        /Users/lfaoro/go/src/github.com/swaggo/swag/gen/gen.go:29 +0x2cc
main.main.func1(0xc4200da2c0, 0xc4204e2100, 0xc4200da2c0)
        /Users/lfaoro/go/src/github.com/swaggo/swag/cmd/swag/main.go:33 +0x190
github.com/urfave/cli.HandleAction(0x1419020, 0x14cdec0, 0xc4200da2c0, 0x0, 0xc420084a20)
        /Users/lfaoro/go/src/github.com/urfave/cli/app.go:501 +0xc8
github.com/urfave/cli.Command.Run(0x14b23b6, 0x4, 0x0, 0x0, 0xc4203bc0f0, 0x1, 0x1, 0x14b534a, 0xe, 0x0, ...)
        /Users/lfaoro/go/src/github.com/urfave/cli/command.go:165 +0x47d
github.com/urfave/cli.(*App).Run(0xc42020a000, 0xc42001e180, 0x4, 0x4, 0x0, 0x0)
        /Users/lfaoro/go/src/github.com/urfave/cli/app.go:259 +0x6e8
main.main()
        /Users/lfaoro/go/src/github.com/swaggo/swag/cmd/swag/main.go:61 +0x4e2
make: *** [doc] Error 2

# lfaoro @ unidentifiedw in ~/go/src/gitlab.com/lfaoro/datacrib on git:master x [15:36:02] C:2
$ make doc
cd srv && swag init -g main.go && cd ..
2018/09/03 15:36:03 Generate swagger docs....
2018/09/03 15:36:03 Generate general API Info
2018/09/03 15:36:07 Generating mdl.Healthz
2018/09/03 15:36:07 Generating mdl.AccountPayload
2018/09/03 15:36:07 Generating mdl.Account
2018/09/03 15:36:07 create docs.go at  docs/docs.go

Expected behavior
Shouldn't panic but display an error

Your swag version
swag version v1.3.2

Additional context
Started doing this behavior after adding this line:
// @Success 201 {object} mdl.Account

type Account struct {
	ID            uuid.UUID  `json:"id" gorm:"primary_key,type:uuid"`
	CreatedAt     time.Time  `json:"created_at,omitempty"`
	UpdatedAt     time.Time  `json:"updated_at,omitempty"`
	DeletedAt     *time.Time `json:"-" sql:"index"`
	IPAddress     string     `json:"ip_address" valid:"ip"` // this validates ipv4 & ipv6
	Status        string     `json:"status" valid:"in(active|inactive)"`
	PaymentStatus string     `json:"payment_status,omitempty" valid:"in(paid|unpaid)"`
	CreditCard    CreditCard `json:"creditcard" valid:""`
	Tokens        int64      `json:"tokens"`
	Balance       int64      `json:"balance"`
	Mac           string     `json:"mac,omitempty"`
	AccountPayload
}

[elvizlai]

same issue on v1.4.0

[psrebniak]

Problem exists when serialized struct has field with time.Time or strfmt.DateTime type.

Minimal code with reproduced error:

package test

import (
	"net/http"
	"time"
)

type DateTime time.Time

type CustomStructure struct {
	Begin DateTime `json:"begin,omitempty"`
}

// @title TEST API

// @Summary Test Endpoint
// @Success 200 {object} test.CustomStructure
// @Router /test [get]
func GetCustomStructure(w http.ResponseWriter, request *http.Request) {}

[rodrigodmd]

@psrebniak I had the same issue and was able to make it work using the "swaggertype" tag:

type DateTime time.Time

type CustomStructure struct {
	Begin DateTime `json:"begin,omitempty"    swaggertype:"primitive,string"`
}

That should help you to compile it as a string. Take a look at https://github.com/swaggo/swag/#override-swagger-type-of-a-struct-field

[easonlin404]

@rodrigodmd ping. Thanks for your comments. Now have to use swaggertype tag to supported custom type declarations like:

type DateTime time.Time

we will add this feat if we have free time, and swag team welcome PR to enhance all of it.