GoでAWS APIを叩く。 aws-sdk-go の 認証には aws.DetectCreds() が便利 ref: http://qiita.com/yamasaki-masahide/items/1a11545e1c5984ab7481

file0.go

var (
    accessKey = "AWSaccesskey"
    secretKey = "AWSsecretKey"
    region    = "ap-northeast-1"
)
func main() {

    httpClient := &http.Client{Timeout: time.Duration(30) * time.Second}

    creds := aws.Creds(accessKey, secretKey, "")
    S3 := s3.New(creds, region, httpClient)

file1.go

    S3 := s3.New(aws.DetectCreds("", "", ""), region, httpClient)

file2.go

package main

import (
        "log"
        "net/http"
        "os"
        "time"

        "github.com/awslabs/aws-sdk-go/aws"
        "github.com/awslabs/aws-sdk-go/gen/s3"
)

var (
        region    = "ap-northeast-1"
        bucket    = "buket_name"
        filename  = "hoge.txt"
        acl       = "private"
        mimeType  = "text/plain"
)

func main() {
        var (
                err  error
                file *os.File
                info os.FileInfo
        )

        httpClient := &http.Client{Timeout: time.Duration(30) * time.Second}

        S3 := s3.New(aws.DetectCreds("", "", ""), region, httpClient)

        if file, err = os.Open(filename); err != nil {
                log.Println(err)
        }
        defer file.Close()

        if info, err = file.Stat(); err != nil {
                log.Println(err)
        }

        req := s3.PutObjectRequest{
                Body:          file,
                Bucket:        &bucket,
                Key:           &filename,
                ACL:           &acl,
                ContentType:   &mimeType,
                ContentLength: aws.Long(info.Size()),
        }

        res, err := S3.PutObject(&req)
        log.Printf("res:%s, err:%s", res, err)

}