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Golang无法在MongoDB中创建文档

来源：stackoverflow 2024-04-19 23:36:32 0浏览收藏

本篇文章给大家分享《Golang无法在MongoDB中创建文档》，覆盖了Golang的常见基础知识，其实一个语言的全部知识点一篇文章是不可能说完的，但希望通过这些问题，让读者对自己的掌握程度有一定的认识(B 数)，从而弥补自己的不足，更好的掌握它。

问题内容

我正在尝试将文档插入 mongodb，但尽管成功连接到 mongo，但我仍然收到以下错误：

http: panic serving 172.27.0.8:40176: runtime error: invalid memory address or nil pointer dereference

我正在初始化数据库连接的 main.go 看起来像这样

func main(){
   
      //connect to mongo
      mongoclient,err:=connecttomongo()
      if err!=nil{
          log.panic(err)
      }
      client=mongoclient
  
      //create a context that mongo needs in order to disconnect
      ctx,_:=context.withtimeout(context.background(), 15*time.second)
     // ctx,cancel:=context.withtimeout(context.background(), 15*time.second)
      //defer cancel()
      
  
      //close connection
      defer func ()  {
          if err =client.disconnect(ctx); err!=nil{
              panic(err)
          }
      }() 

    muxrouter := mux.newrouter().strictslash(true)

    //specify who's allowed to connect
    c:=cors.new(cors.options{ 
        allowedorigins: []string{"https://*", "http://*"},
        allowedmethods: []string{"get", "post", "put", "delete", "options"},
        allowedheaders: []string{"accept", "authorization", "content-type", "x-csrf-token"},
        exposedheaders: []string{"link"},
        allowcredentials: true,
        maxage: 300,
})
    router := addroutes(muxrouter)
    handler := c.handler(router)
    log.println("service stratring at o  port ",webport)

    sterr := http.listenandserve(":9090", handler) //uncomment this line when using docker
    if sterr != nil {
        log.fatal("error starting http server :: ", err)
        return
    }

    log.println("service started at port ",webport)


    
  

}

func connecttomongo()(*mongo.client,error){
    mongousername := os.getenv("mongousername")
    mongopassword := os.getenv("mongopassword")
    //create connection options
    clientoptions:=options.client().applyuri(mongourl)
    clientoptions.setauth(options.credential{
        username: mongousername,
        password: mongopassword,
    })

    //connect
    c,err:=mongo.connect(context.todo(),clientoptions)
    if err!=nil{
        log.println("error connecting to mongo",err)
        return nil,err
    }
    log.println("connected to mongo")
    return c,nil
}

在一个单独的文件 models.go 中，我尝试将数据插入数据库，如下所示：

var client *mongo.Client
func  Insert(entry LogEntry)error{
    log.Printf("Attempting to insert %s", entry)
    log.Printf("client s  %s", client)
    //db:=client.Database("logs")
    //log.Printf("database  is  %s", db)
    
   collection:=client.Database("logs").Collection("logsCollection")
    log.Printf("collection is  %s", collection)

    _,err :=collection.InsertOne(context.TODO(), LogEntry{
        Name: entry.Name,
        Data: entry.Data,
        CreatedAt: time.Now(),
        UpdatedAt: time.Now(),
    })
    if err!=nil{
        log.Println("Error inserting new record into logs collection",err)
        return err
    }
    log.Println("insert successful")
    return nil
}

有人能发现我做错了什么吗？

正确答案

由于错误是通用的（例如，未提供错误的行号），我将分享一个可行的解决方案，也许可以帮助您找出问题所在。我先分享一下代码。

`main.go` 文件

package main

import (
    "context"
    "fmt"
    "time"

    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

type LogEntry struct {
    Name      string
    Data      string
    CreatedAt time.Time
    UpdatedAt time.Time
}

func main() {
    ctx, cancel := context.WithTimeout(context.Background(), time.Second*20)
    defer cancel()

    clientOptions := options.Client().ApplyURI("mongodb://root:root@localhost:27017")
    mongoClient, err := mongo.Connect(ctx, clientOptions)
    if err != nil {
        panic(err)
    }
    defer mongoClient.Disconnect(ctx)

    demoDb := mongoClient.Database("demodb")
    myCollection := demoDb.Collection("myCollection")

    // delete documents
    if _, err := myCollection.DeleteMany(ctx, bson.M{}); err != nil {
        panic(err)
    }

    // insert data
    insertRes, err := myCollection.InsertOne(ctx, LogEntry{
        Name:      "lorem ipsum",
        Data:      "lorem ipsum",
        CreatedAt: time.Now(),
        UpdatedAt: time.Now(),
    })
    if err != nil {
        panic(err)
    }
    fmt.Println(insertRes.InsertedID)

    // query data
    cursor, err := myCollection.Find(ctx, bson.M{})
    if err != nil {
        panic(err)
    }
    var logEntries []bson.M
    if err = cursor.All(ctx, &logEntries); err != nil {
        panic(err)
    }
    for _, v := range logEntries {
        fmt.Println(v)
    }
}

为了演示，我将所有逻辑放在一个文件中。在此文件中，我执行了以下步骤：