svc := s3.New(session.New(), aws.NewConfig().WithRegion("ap-northeast-1"))

req, _ := svc.GetObjectRequest(&s3.GetObjectInput{
    Bucket: aws.String("bucket_name"),
    Key:    aws.String("file_path"),
})
url, err := req.Presign(time.Hour * 2) // 有効期限を指定して署名付きURLを取得
if err != nil {
    fmt.Println("Failed to sign request", err)
}

fmt.Println(url)