golang gin-gonic and splitting files in package

Question

I am quite new to go and try to learn, I am setting up an application with a gin-gonic server. I managed to have it to work with everything in on main package, I would like to organize it better with all the apirest related in a package (which I manage) AND to split each group CRUD by file.

so in the "main" file of the package within the init function, I defined :

Router := gin.New()
Router.Use(gin.Logger())
Router.Use(gin.Recovery())

and I though that I would be able in each other files of the package to use it like that :

v1 := Router.Group("/api/v1/todos")
v1.Use(AuthRequired())
{
    v1.POST("/", CreateTodo)
    v1.GET("/", FetchAllTodo)
    v1.GET("/:id", FetchSingleTodo)
    v1.PUT("/:id", UpdateTodo)
    v1.DELETE("/:id", DeleteTodo)
}

or

packagename.Router.Group

but none are working and I get :

undefined: Router in Router.Group

Stéphane PS : I did setup a sub folder for the package and I am able to go build it if it's in one file.

---

I though that the solution was to declare the Router variable as *gin.Engine but while it's compiling fine, I get a panic error on the Router.Group call

let me post some more part of code :

maincode.go :

package main

import (
    "fmt"
    "./apirest"
    "github.com/braintree/manners"
)

func main(){
    fmt.Printf("hello world.\n")
    //router.Run()
    manners.ListenAndServe(":8080", apirest.Router)
}

Then I split the apirest package in 2 files :

apirest.go (I did manually cleanup, maybee I missed an import) :

package apirest

import (
    "fmt"
    "github.com/gin-gonic/gin"
    "github.com/braintree/manners"
    "os"
    "os/signal"
)

//Router pour gérer l'api
var Router *gin.Engine

/*
    MAIN FUNCTION
*/
func init() {

    Router := gin.New()
    Router.Use(gin.Logger())
    Router.Use(gin.Recovery())

    c := make(chan os.Signal, 1)
    signal.Notify(c, os.Interrupt)
    go func(){
        for sig := range c {
            // sig is a ^C, handle it
            fmt.Printf("ctl+c catched "+sig.String())
            manners.Close()
        }
    }()

    LoadMonitor()

}

and then the todoCRUD.go file that handle all the declaration, the todoCRUD.go and apirest.go are in the same subfolder apirest (and compile ok) :

package apirest

import (
    "fmt"
    "github.com/gin-gonic/gin"
    "gopkg.in/validator.v2"
    "github.com/jinzhu/gorm"
    "strconv"
    "net/http"
    "time"
)

//Todo definition d'un element todo
type Todo struct {
    gorm.Model
    CreatedAt   time.Time
    UpdatedAt   time.Time
    OwnerID     int    `json:"ownerid"  validate:"nonzero"`
    URL         string `json:"url"`
}

//TransformedTodo version pour le retour d'api sans certaines infos
type TransformedTodo struct {
    ID          uint   `json:"id"`
    CreatedAt   time.Time
    UpdatedAt   time.Time
    OwnerID     uint   `json:"ownerid"`
    URL         string `json:"url"`   
}

//LoadTodo permet de lancer le mappage todos
func LoadTodo(){
    v1 := Router.Group("/api/v1/todos")
    {
        v1.POST("/", CreateTodo)
        v1.GET("/", FetchAllTodo)
        v1.GET("/:id", FetchSingleTodo)
        v1.PUT("/:id", UpdateTodo)
        v1.DELETE("/:id", DeleteTodo)
    }
}

//CreateTodo génération d'un todo
func CreateTodo(c *gin.Context) {

    owner, _ := strconv.Atoi(c.PostForm("ownerid"))
    todo := Todo{
        OwnerID: owner,
        URL: c.PostForm("url"),
    };
    v := validator.NewValidator()
    if errs := v.Validate(todo); errs!=nil {
        errors := errs.(validator.ErrorMap)
        var errOuts []string
        for f, e := range errors {
            errOuts = append(errOuts, fmt.Sprintf("\t - %s (%v)\n", f, e))
        }
        //c.JSON(500, gin.H{"Error": errs.Error()})
        c.JSON(500, gin.H{"Erreur sur le(s) champ(s) : ": errOuts})
    } else {

        db, _ := Database()
        defer db.Close()
        db.Save(&todo)

        c.JSON(http.StatusCreated, gin.H{"status" : http.StatusCreated, "message" : "Todo item created successfully!", "resourceId": todo.ID})
    }
}

//FetchAllTodo récupération de tous les todos
func FetchAllTodo(c *gin.Context) {
    var todos []Todo
    var _todos []TransformedTodo

    db, _ := Database()
    defer db.Close()
    db.Find(&todos)

    if (len(todos) <= 0) {
        c.JSON(http.StatusNotFound, gin.H{"status" : http.StatusNotFound, "message" : "No todo found!"})
        return
    }

    //transforms the todos for building a good response,
    //je peux choisir des champs a ne pas display
    for _, item := range todos {
        status := false
        if (item.Status == 1) {
            status = true
        } else {
            status = false
        }
        _todos = append(_todos, TransformedTodo{ID: item.ID, URL:item.URL})
    }
    c.JSON(http.StatusOK, gin.H{"status" : http.StatusOK, "data" : _todos})
}

//FetchSingleTodo Récupération d'un seul todo en fonction de son id
func FetchSingleTodo(c *gin.Context) {
    var todo Todo
    todoID := c.Param("id")

    db, _ := Database()
    defer db.Close()
    db.First(&todo, todoID)

    if (todo.ID == 0) {
        c.JSON(http.StatusNotFound, gin.H{"status" : http.StatusNotFound, "message" : "No todo found!"})
        return
    }

    _todo := TransformedTodo{ID: todo.ID, URL:todo.URL}
    c.JSON(http.StatusOK, gin.H{"status" : http.StatusOK, "data" : _todo})
}

//UpdateTodo Mise à jour d'un todo
func UpdateTodo(c *gin.Context) {
    var todo Todo
    todoID := c.Param("id")
    db, _ := Database()
    defer db.Close()
    db.First(&todo, todoID)

    if (todo.ID == 0) {
        c.JSON(http.StatusNotFound, gin.H{"status" : http.StatusNotFound, "message" : "No todo found!"})
        return
    }

    db.Model(&todo).Update("title", c.PostForm("title"))
    db.Model(&todo).Update("completed", c.PostForm("completed"))
    c.JSON(http.StatusOK, gin.H{"status" : http.StatusOK, "message" : "Todo updated successfully!"})
}


//DeleteTodo Suppression d'un todo
func DeleteTodo(c *gin.Context) {
    var todo Todo
    todoID := c.Param("id")
    db, _ := Database()
    defer db.Close()
    db.First(&todo, todoID)

    if (todo.ID == 0) {
        c.JSON(http.StatusNotFound, gin.H{"status" : http.StatusNotFound, "message" : "No todo found!"})
        return
    }

    db.Delete(&todo)
    c.JSON(http.StatusOK, gin.H{"status" : http.StatusOK, "message" : "Todo deleted successfully!"})
}

The Idea is to have a xxxxCRUD.go file for each entity to handle but the whole folder in the same package.

the exact errror is :

PS D:\www\developpement> go run .\maincode.go [GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production. - using env: export GIN_MODE=release - using code: gin.SetMode(gin.ReleaseMode)

panic: runtime error: invalid memory address or nil pointer dereference [signal 0xc0000005 code=0x0 addr=0x0 pc=0x46cc0f]

goroutine 1 [running]: panic(0x831880, 0xc04200a080) C:/Go/src/runtime/panic.go:500 +0x1af /D/www/developpement/apirest.LoadTodo() D:/www/developpement/apirest/todoCRUD.go:33 +0x2f [Router.Group] /D/www/developpement/apirest.init.1() D:/www/developpement/apirest/apirest.go:73 +0x220 [LoadTodo()] /D/www/developpement/apirest.init() D:/www/developpement/apirest/todoCRUD.go:190 +0x80 [last line] main.init() D:/www/developpement/maincode.go:13 +0x3a [manners.ListenAndServe(":8080", apirest.Router)] exit status 2

I hope that this will help to understand !

Thanks for your time and help !

Stéphane

Answer 1

I did manage to make it work by "sending" the router in the LoadTodo function :

in apirest.go :

LoadTodo(Router)

and in todoCRUD.go :

func LoadTodo(r *gin.Engine){

and it's working fine ... I hope I didn't bring a bug failure in the code ...

Stéphane