Gorm Panic golang : panic serving runtime error: invalid memory address or nil pointer dereference

I'm trying to solve this panic error, i'm just created a backend in GOLANG, that code was my first steps, also if u see some mistakes, tell me!.

Here was the firts part of code , the Main: (main.go) into the package main:

if you see we have 2 functions

• main()

• BindRoutes(function()) -> it recieves a binder when it's called from the main

  func main() {
  err := godotenv.Load(".env")
  if err != nil {
  log.Fatal(err)
  }
  // Variables de la base de datos para el struct
  host := os.Getenv("POSTGRES_HOST")
  user := os.Getenv("POSTGRES_USER")
  port := os.Getenv("POSTGRES_PORT")
  password := os.Getenv("POSTGRES_PASSWORD")
  dbname := os.Getenv("POSTGRES_DB")
  // Variables del servidor
  PORT := os.Getenv("PORT")
  JWT_SECRET := os.Getenv("JWT_SECRET")
  DB_URL := os.Getenv("DATA_BASE_URL")
  server, err := server.NewServer(context.Background(), &server.Config{
  JWTSecret:   JWT_SECRET,
  Port:        PORT,
  DatabaseUrl: DB_URL,
  })
  if err != nil {
  log.Fatal(err)
  }
  db := config.Database{
  Host:     host,
  Port:     port,
  User:     user,
  Password: password,
  Dbname:   dbname,
  }
  db.Open()
  server.Start(BindRoutes)
  }
  func BindRoutes(s server.Server, r *mux.Router, db *config.Database) {
  r.HandleFunc("/blog/newblog", handler.CreateNewBlog(s, db)).Methods(http.MethodPost)
  }
  

Next we have the SERVER package

Here we have 2 structs and 1 interface, there the most important part is the binder, there I don't know if i implemented good.

```
package server
import (
"context"
"errors"
"log"
"net/http"
"github.com/felipeolayao1998/backdiariodeuninge/config"
"github.com/gorilla/mux"
)
type Config struct {
Port        string
JWTSecret   string
DatabaseUrl string
}
type Server interface {
Config() *Config
}
type Broker struct {
config *Config
router *mux.Router
}
func (b *Broker) Config() *Config {
return b.config
}
func NewServer(ctx context.Context, config *Config) (*Broker, error) {
if config.Port == "" {
return nil, errors.New("port is required")
}
if config.JWTSecret == "" {
return nil, errors.New("jwt secret is required")
}
if config.DatabaseUrl == "" {
return nil, errors.New("database url is required")
}
broker := &Broker{
config: config,
router: mux.NewRouter(),
}
return broker, nil
}
func (b *Broker) Start(binder func(s Server, r *mux.Router, db *config.Database)) {
b.router = mux.NewRouter()
binder(b, b.router, &config.Database{})
log.Println("starting server on port", b.config.Port)
if err := http.ListenAndServe(b.config.Port, b.router); err != nil {
log.Println("error starting server:", err)
} else {
log.Fatalf("server stopped")
}
}
```

Models:

```
package Models
type Blog struct {
Id      string `json:"id" gorm:"type:string;default:string;primary_key;unique"`
Name    string `json:"name" gorm:"type:varchar(255);not null"`
Content string `json:"content" gorm:"type:varchar(2000);not null"`
Likes   int    `json:"likes" gorm:"type:integer" `
}
```

Handler:
Here i have the problem, when i call the create, it returns an PANIC as you can see at the end of this question.

   func CreateNewBlog(s server.Server, db *config.Database) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-type", "application/json")
w.WriteHeader(http.StatusOK)
db.Db.Create(&models.Blog{Id: "1", Name: "Felipe", Content: "fdasfasfa", Likes: 1}) //Here is the problem
}
}
2023/04/07 21:25:46 starting server on port :8000
0xc00043a028 &{a2081199-a75e-4b3e-9551-3442a0fe0d21 Felipe contenido ejempo 1}
2023/04/07 21:25:55 http: panic serving [::1]:59553: runtime error: invalid memory address or nil pointer dereference
goroutine 18 [running]:
net/http.(*conn).serve.func1()
C:/Program Files/Go/src/net/http/server.go:1850 +0xbf
panic({0x1620000, 0x1c52680})
C:/Program Files/Go/src/runtime/panic.go:890 +0x262
gorm.io/gorm.(*DB).Create(0x17e44c0?, {0x15d11c0?, 0xc00041c180?})
C:/Users/Bymet/go/pkg/mod/gorm.io/gorm@v1.24.7-0.20230306060331-85eaf9eeda11/finisher_api.go:18 +0x22
github.com/felipeolayao1998/backdiariodeuninge/handler.CreateNewBlog.func1({0x17ea340, 0xc000424000}, 0xc00042c100)
D:/PodCast/PaginaWeb/backend/handler/handlerBlog.go:69 +0x3e5 
</details>
# 答案1
**得分**: 2
你正在将一个未初始化的指针传递给`db`变量的`Db`字段的`Create`方法。
你可以尝试先初始化db连接。
```go
func CreateNewBlog(s server.Server, db *config.Database) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-type", "application/json")
w.WriteHeader(http.StatusOK)
// 初始化数据库连接
err := db.Open()
if err != nil {
log.Fatal(err)
}
// 在数据库中创建一个新的博客记录
db.Db.Create(&models.Blog{Id: "1", Name: "Felipe", Content: "fdasfasfa", Likes: 1})
}
}

func CreateNewBlog(s server.Server, db *config.Database) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-type", "application/json")
w.WriteHeader(http.StatusOK)
// Initialize the database connection
err := db.Open()
if err != nil {
log.Fatal(err)
}
// Create a new blog record in the database
db.Db.Create(&models.Blog{Id: "1", Name: "Felipe", Content: "fdasfasfa", Likes: 1})
}