Golang cannot create document in MongoDB

Question content

I'm trying to insert a document into mongodb, but despite successfully connecting to mongo, I still get the following error:

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

My main.go which is initializing the database connection looks like this

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
}

In a separate file models.go, I try to insert data into the database like this:

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
}

Can anyone spot what I'm doing wrong?

Workaround

Since the error is generic (e.g. wrong line number not provided), I'll share a possible solution that might help you figure out the problem. Let me share the code first.

main.go File

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)
    }
}

For demonstration, I put all the logic in one file. In this file I performed the following steps:

1. Set up mongodb connection.
2. Connect to a database and collections in that database.
3. Delete all existing documentation (just for clarity).
4. Insert a new logentry instance into the mycollection collection.
5. Retrieve all items in mycollection collection.

The last thing to mention is the docker command I use to run the container:

docker run -d -p 27017:27017 --name mymongo -e mongo_initdb_root_username=root -e mongo_initdb_root_password=root mongo:latest

If you stick with my solution, you should be able to insert the document without any problems. If not, please let me know and I'll try to help you!

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