Connecting Gorm and Gin Golang - go

Question

I am trying to create an API with Go, gorm and gin. However, using a direct SQL query did work, but it became too cumbersome and I decided to leverage gorm which is fantastic. However after my implementation, I am unable to get the project up again and keep getting error
panic: runtime error: invalid memory address or nil pointer
dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0xb0
pc=0x137b606]
I have pasted my code with packages here. I would be glad if someone could point me to the issue.
PostgresDoa.go
package postgres
import (
"fmt"
"log"
"net/http"
"github.com/AdieOlami/bookstore_users-api/domain/users"
"github.com/gin-gonic/gin"
"github.com/jinzhu/gorm"
)
type Sever struct {
DB *gorm.DB
Router *gin.Engine
}
func (server *Sever) Initialize(Dbdriver, DbUser, DbPassword, DbPort, DbHost, DbName string) {
var err error
if Dbdriver == "mysql" {
DBURL := fmt.Sprintf("%s:%s#tcp(%s:%s)/%s?charset=utf8&parseTime=True&loc=Local", DbUser, DbPassword, DbHost, DbPort, DbName)
server.DB, err = gorm.Open(Dbdriver, DBURL)
if err != nil {
fmt.Printf("Cannot connect to %s database", Dbdriver)
log.Fatal("This is the error:", err)
} else {
fmt.Printf("We are connected to the %s database", Dbdriver)
}
}
if Dbdriver == "postgres" {
DBURL := fmt.Sprintf("host=%s port=%s user=%s dbname=%s sslmode=disable password=%s", DbHost, DbPort, DbUser, DbName, DbPassword)
server.DB, err = gorm.Open(Dbdriver, DBURL)
if err != nil {
fmt.Printf("Cannot connect to %s database", Dbdriver)
log.Fatal("This is the error:", err)
} else {
fmt.Printf("We are connected to the %s database", Dbdriver)
}
}
server.DB.Debug().AutoMigrate(&users.User{}) //database migration
server.Router = gin.Default()
}
func (server *Sever) Run(addr string) {
fmt.Println("Listening to port 8080")
log.Fatal(http.ListenAndServe(addr, server.Router))
}
UserDto.go
package users
import (
"strings"
"github.com/AdieOlami/bookstore_users-api/domain/base"
"github.com/AdieOlami/bookstore_users-api/utils/errors"
"github.com/jinzhu/gorm"
uuid "github.com/satori/go.uuid"
)
type User struct {
base.Base
UserID uuid.UUID `gorm:"type:uuid;column:userId;not null;" json:"userId"`
FirstName string `gorm:"size:255;not null;unique;column:firstName" json:"firstName"`
LastName string `gorm:"size:255;not null;unique;column:lastName" json:"lastName"`
Email string `gorm:"size:100;not null;unique;column:email" json:"email"`
}
func (user *User) Validate() *errors.Error {
user.Email = strings.TrimSpace(strings.ToLower(user.Email))
if user.Email == "" {
return errors.NewBadRequestError("invalid email address")
}
return nil
}
func (user *User) SaveUser(db *gorm.DB) *errors.Error {
var err error
err = db.Debug().Create(&user).Error
if err != nil {
return errors.NewInteralServerError(err.Error())
}
return nil
}
UserService.go
package services
import (
"github.com/AdieOlami/bookstore_users-api/domain/users"
"github.com/AdieOlami/bookstore_users-api/utils/errors"
)
func (server *Server) CreateUser(user users.User) (*users.User, *errors.Error) {
if err := user.Validate(); err != nil {
return nil, err
}
if err := user.SaveUser(server.DB); err != nil {
return nil, err
}
return &user, nil
}
UserController.go
package users
import (
"net/http"
"strconv"
"github.com/AdieOlami/bookstore_users-api/domain/users"
"github.com/AdieOlami/bookstore_users-api/services"
"github.com/AdieOlami/bookstore_users-api/utils/errors"
"github.com/gin-gonic/gin"
)
var (
server = services.Server{}
)
// CREATE USER
func CreateUser(c *gin.Context) {
var user users.User
if err := c.ShouldBindJSON(&user); err != nil {
// TODO: hnadle json error return bad request
err := errors.NewBadRequestError("invalid json body")
c.JSON(err.Status, err)
// fmt.Println(err.Error())
return
}
result, saveErr := server.CreateUser(user)
if saveErr != nil {
// TODO: handle user createing error
c.JSON(saveErr.Status, saveErr)
return
}
c.JSON(http.StatusCreated, result)
}
Routes.go
package app
import (
"github.com/AdieOlami/bookstore_users-api/controllers/users"
"github.com/AdieOlami/bookstore_users-api/database/postgres"
)
var (
server = postgres.Sever{}
)
func initializeRoutes() {
server.Router.POST("/users", users.CreateUser)
}
Application.go
package app
import (
"os"
"github.com/AdieOlami/bookstore_users-api/seed"
_ "github.com/jinzhu/gorm/dialects/mysql" //mysql database driver
_ "github.com/jinzhu/gorm/dialects/postgres" //postgres database driver
)
func StartApplication() {
server.Initialize(os.Getenv("DB_DRIVER"), os.Getenv("DB_USER"), os.Getenv("DB_PASSWORD"), os.Getenv("DB_PORT"), os.Getenv("DB_HOST"), os.Getenv("DB_NAME"))
seed.Load(server.DB)
server.Run(":8088")
initializeRoutes()
}
in my Main.go
func main() {
app.StartApplication()
}

Answer 1

As far as I can understand from your code. You declared below function in Services package whereas Server object is declared in the Postgres package. This causes dereferencing of pointer server *Server to an invalid address. you have to declare this function in posgres package.
func (server *Server) CreateUser(user users.User) (*users.User, *errors.Error) {
if err := user.Validate(); err != nil {
return nil, err
}
if err := user.SaveUser(server.DB); err != nil {
return nil, err
}
return &user, nil
}