problem reading file from s3 using golang with lambda

I have the following code in golang for read a file and extract some colums of the file, the fileName is received from my lambda, but in my first step that is get the file from s3 i am getting a problem.

My code is:

package main
import (
"fmt"
"packageXXX/cmd/utils"
"github.com/aws/aws-lambda-go/lambda"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/s3"
"github.com/aws/aws-sdk-go/service/s3/s3manager"
"go.uber.org/zap"
)
var (
log *zap.Logger
)
func init() {
log = utils.InitLogger()
}
func DownloadFile(downloader *s3manager.Downloader, bucketName string, key string) error {
buff := &aws.WriteAtBuffer{}
numBytes, err := downloader.Download(
buff,
&s3.GetObjectInput{
Bucket: aws.String(bucketName),
Key:    aws.String(key),
},
)
data := buff.Bytes() // now data is my []byte array
log.Info("nnnnnnnnnnnnnnn", zap.Any("nnn", numBytes))
log.Info("xxxxxxxxxxxxxxx", zap.Any("bytes", data))
return err
}
func handler(fileName string) (string, error) {
log.Info(fmt.Sprintf("received: %s", fileName))
sess, err := session.NewSessionWithOptions(session.Options{
Profile: "default",
Config: aws.Config{
Region: aws.String("us-west-2"),
},
})
if err != nil {
log.Info("errorrrrrrrrr", zap.Any("session", err))
return "errorr,", nil
} else {
log.Info("sessionnnnnnnnnnnnnn", zap.Any("sess", sess))
}
bucketName := "s3-test-lambda-go-xxx"
downloader := s3manager.NewDownloader(sess)
log.Info("downloader", zap.Any("downloader", err))
key := fileName
err = DownloadFile(downloader, bucketName, key)
if err != nil {
fmt.Printf("Couldn't download file: %v", err)
return "errror", nil
}
fmt.Println("Successfully downloaded file")
return fmt.Sprintf("el file recibido es: %s", fileName), nil
}
func main() {
lambda.Start(handler)
}

And the log that is printing is:

For verbose messaging see aws.Config.CredentialsChainVerboseErrorsSTART RequestId: dba8ebd5-9102-4a2f-8e45-cdef355f1bbd Version: $LATEST
{"level":"info","ts":"2022-11-02T17:31:32Z","msg":"received: gggggg2.txt"}
{"level":"info","ts":"2022-11-02T17:31:32Z","msg":"sessionnnnnnnnnnnnnn","sessError":"json: unsupported type: endpoints.endpointDefaults"}
{"level":"info","ts":"2022-11-02T17:31:32Z","msg":"downloader","downloader":null}
{"level":"info","ts":"2022-11-02T17:31:38Z","msg":"nnnnnnnnnnnnnnn","nnn":0}
{"level":"info","ts":"2022-11-02T17:31:38Z","msg":"xxxxxxxxxxxxxxx","bytes":""}
Couldn't download file: NoCredentialProviders: no valid providers in chain. Deprecated.
END RequestId: dba8ebd5-9102-4a2f-8e45-cdef355f1bbd

The problem is the session

Then Is possible create session with role, because like is production i don't want use access and secret key?
Thanks a lot

Session will load your default session if you but it like this

sess, err := session.NewSession(&aws.Config{
  Region: aws.String("us-east-1")},
)

instead of:

    sess, err := session.NewSessionWithOptions(session.Options{
        Profile: "default",
        Config: aws.Config{
            Region: aws.String("us-west-2"),
        },
    })

This means it will use whatever session you have configured not depending on whether you are inside the lambda or local. This also means you can assume any role you want to assume or even use SSO to login (so no access key and secret are required).