Opening a change stream cursor for any database in go using mongo-go-driver, gives error on cursor decoding.

mongo-go-driver-bug.go

package main

import (
	"context"
	"fmt"
	"github.com/mongodb/mongo-go-driver/bson"
	"github.com/mongodb/mongo-go-driver/mongo"
	"log"
)

const (
	config = `mongodb://127.0.0.1:27017`
	DB     = `testdb`
	COL    = `col`
)

func errLogs(err error) {
	if err != nil {
		log.Println(err)
	}
}

func traverseCursor(ctx context.Context, cur mongo.Cursor) {
	for cur.Next(ctx) {
		ele := bson.M{}

		err := cur.Decode(&ele)
		errLogs(err)

		fmt.Println(ele)
	}
}

/*
Run this Query:
	use testdb;
	db.col.insertOne( { name: "Shivam" } );

and the following function (watchOnDB) will panic out with the message:
	panic: runtime error: invalid memory address or nil pointer dereference
	[signal SIGSEGV: segmentation violation code=0x1 addr=0x58 pc=0x779242]

	goroutine 1 [running]:
	github.com/mongodb/mongo-go-driver/mongo.(*changeStream).Decode(0xc000118000, 0x7bb880, 0xc000116028, 0xc0000cfe01, 0x42ad92)
		$GOPATH/src/github.com/mongodb/mongo-go-driver/mongo/change_stream.go:454 +0x62
	main.traverseCursor(0x979100, 0xc00001e0f0, 0x97a0c0, 0xc000118000)
		.../main.go:27 +0x48
	main.watchOnDB(0x979100, 0xc00001e0f0, 0xc000093400, 0x84e5bc, 0x6)
		.../main.go:68 +0x1dc
	main.main()
		.../main.go:81 +0x119

	Process finished with exit code 2
*/

func watchOnDB(ctx context.Context, cli *mongo.Client, _db string) {

	fmt.Printf("Starting change stream watch on database %s.\n", _db)

	db := cli.Database(_db)

	var p interface{}
	cur, err := db.Watch(ctx, p)
	errLogs(err)
	defer cur.Close(ctx)

	traverseCursor(ctx, cur)
}

func main() {
	ctx := context.Background()

	cli, err := mongo.NewClient(config)
	errLogs(err)

	errLogs(cli.Connect(ctx))

	defer cli.Disconnect(ctx)

	watchOnDB(ctx, cli, DB)

}