golangでS3からGetObjectする

• はじめに

github.com/aws/aws-sdk-go このsdkを使ったs3オブジェクトの取得を行うサンプルコードです。

• sample

package main

import (
    "fmt"
    "os"

    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/credentials"
    "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"
)

//ダウンロードするオブジェクトの構造体
type downloader struct {
    *s3manager.Downloader
    bucket string
    file   string
    dir    string
}

func main() {
    accessKeyId := "AccessKeyId"
    secretAccessKey := "SecretAccessKey"

    // The session the S3 Downloader will use
    sess := session.Must(session.NewSession(
        &aws.Config{
            Credentials: credentials.NewStaticCredentials(accessKeyId, secretAccessKey, ""),
            Region:      aws.String("ap-northeast-1"),
        }))

    // Create a downloader with the session and default options
    downloader := s3manager.NewDownloader(sess)

    localFilename := "download.tar"
    // Create a file to write the S3 Object contents to.
    f, err := os.Create(localFilename)
    if err != nil {
        fmt.Printf("failed to create file %q, %v", localFilename, err)
    }

    bucketName := "BacketName"
    key := "targetFileName"

    // Write the contents of S3 Object to the file
    n, err := downloader.Download(f, &s3.GetObjectInput{
        Bucket: aws.String(bucketName),
        Key:    aws.String(key),
    })

    if err != nil {
        fmt.Printf("failed to download file, %v", err)
    }
    fmt.Printf("file downloaded, %d bytes\n", n)
}

• tips

このerror

cannot use \"ap-northeast-1\" (type string) as type *string in field value

   // The session the S3 Downloader will use
    sess := session.Must(session.NewSession(
        &aws.Config{
            Credentials: credentials.NewStaticCredentials(accessKeyId, secretAccessKey, ""),
            Region:      "ap-northeast-1",
        }))

stringを*string(ポインタ)に変換して、ということらしい。

確かにRegion *stringこうなってます。

Config_struct

ググったらaws.String()というのもがあることがわかったので、修正しました。

   // The session the S3 Downloader will use
    sess := session.Must(session.NewSession(
        &aws.Config{
            Credentials: credentials.NewStaticCredentials(accessKeyId, secretAccessKey, ""),
            Region:      aws.String("ap-northeast-1"),
        }))

ポインタは値をコピーせずアドレスを渡すらしい。

おわり