Q:

How to get AWS credentials and access to S3 on Docker

I'm setting up Docker containers. 
On the server side, files are uploaded to S3. 
It succeeded to upload under my local environment. 
However, it fails to upload under Docker environment.

client: React/axios
server: Golang/gin
db: mysql
source code: https://github.com/jpskgc/article

article
　├ client
　├ api  
　└ docker-compose.yml

Here is the docker-compose.yml:
version: '3'
services:
  api:
    build:
      dockerfile: Dockerfile.dev
      context: ./api
    volumes:
      - ./api:/app
    ports:
      - 2345:2345
    depends_on:
      - db
    tty: true
    volumes:
      - $HOME/.aws/credentials.properties:/home/api/.aws/credentials.properties

Here is the server side code to access to S3.
api := router.Group("/api")
{
    api.POST("/post/image", func(c *gin.Context) {
        var creds *credentials.Credentials
        var err error

        creds = credentials.NewSharedCredentials("", "default")
        _, err = creds.Get()

        if err != nil {
            creds = credentials.NewCredentials(&ec2rolecreds.EC2RoleProvider{})
            _, err = creds.Get()
        }

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

        form, _ := c.MultipartForm()

        files := form.File["images[]"]

        var imageNames []ImageName
        imageName := ImageName{}

        for _, file := range files {

            f, err := file.Open()

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

            defer f.Close()

            size := file.Size
            buffer := make([]byte, size)

            f.Read(buffer)
            fileBytes := bytes.NewReader(buffer)
            fileType := http.DetectContentType(buffer)
            path := "/media/" + file.Filename
            params := &s3.PutObjectInput{
                Bucket:        aws.String("article-s3-jpskgc"),
                Key:           aws.String(path),
                Body:          fileBytes,
                ContentLength: aws.Int64(size),
                ContentType:   aws.String(fileType),
            }
            resp, err := svc.PutObject(params)

            fmt.Printf("response %s", awsutil.StringValue(resp))

            imageName.NAME = file.Filename

            imageNames = append(imageNames, imageName)
        }

        c.JSON(http.StatusOK, imageNames)
    })
}

I expect images are uploaded in server side to S3. 
But in actuality they're not. 
Here are some logs:
api_1     | 2019/07/31 14:58:53 [Recovery] 2019/07/31 - 14:58:53 panic recovered:
api_1     | POST /api/post/image HTTP/1.1
api_1     | Host: localhost:2345
api_1     | Accept: application/json, text/plain, */*
api_1     | Accept-Encoding: gzip, deflate, br
api_1     | Accept-Language: en-US,en;q=0.9
api_1     | Connection: keep-alive
api_1     | Content-Length: 92267
api_1     | Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryYx6aOI06AYceIHnU
api_1     | Origin: http://localhost:3000
api_1     | Referer: http://localhost:3000/post/finish
api_1     | User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.142 Safari/537.36
api_1     | 
api_1     | 
api_1     | runtime error: invalid memory address or nil pointer dereference
api_1     | /usr/local/go/src/runtime/panic.go:82 (0x4427f0)
api_1     |     panicmem: panic(memoryError)
api_1     | /usr/local/go/src/runtime/signal_unix.go:390 (0x44261f)
api_1     |     sigpanic: panicmem()
api_1     | /go/src/github.com/aws/aws-sdk-go/aws/ec2metadata/api.go:26 (0xa01a35)
api_1     |     (*EC2Metadata).GetMetadata: req := c.NewRequest(op, nil, output)
api_1     | /go/src/github.com/aws/aws-sdk-go/aws/credentials/ec2rolecreds/ec2_role_provider.go:134 (0xa05607)
api_1     |     requestCredList: resp, err := client.GetMetadata(iamSecurityCredsPath)
api_1     | /go/src/github.com/aws/aws-sdk-go/aws/credentials/ec2rolecreds/ec2_role_provider.go:90 (0xa05159)
api_1     |     (*EC2RoleProvider).Retrieve: credsList, err := requestCredList(m.Client)
api_1     | /go/src/github.com/aws/aws-sdk-go/aws/credentials/credentials.go:241 (0x945246)
api_1     |     (*Credentials).Get: creds, err := c.provider.Retrieve()
api_1     | /app/main.go:172 (0xb1dde1)
api_1     |     main.func5: _, err = creds.Get()
api_1     | /go/src/github.com/gin-gonic/gin/context.go:147 (0x8f97c9)
api_1     |     (*Context).Next: c.handlers[c.index](c)
api_1     | /go/src/github.com/gin-gonic/gin/recovery.go:83 (0x90d259)
api_1     |     RecoveryWithWriter.func1: c.Next()
api_1     | /go/src/github.com/gin-gonic/gin/context.go:147 (0x8f97c9)
api_1     |     (*Context).Next: c.handlers[c.index](c)
api_1     | /go/src/github.com/gin-gonic/gin/logger.go:240 (0x90c300)
api_1     |     LoggerWithConfig.func1: c.Next()
api_1     | /go/src/github.com/gin-gonic/gin/context.go:147 (0x8f97c9)
api_1     |     (*Context).Next: c.handlers[c.index](c)
api_1     | /go/src/github.com/gin-gonic/gin/gin.go:391 (0x9036c9)
api_1     |     (*Engine).handleHTTPRequest: c.Next()
api_1     | /go/src/github.com/gin-gonic/gin/gin.go:352 (0x902dbd)
api_1     |     (*Engine).ServeHTTP: engine.handleHTTPRequest(c)
api_1     | /usr/local/go/src/net/http/server.go:2774 (0x6dcc77)
api_1     |     serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
api_1     | /usr/local/go/src/net/http/server.go:1878 (0x6d8860)
api_1     |     (*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
api_1     | /usr/local/go/src/runtime/asm_amd64.s:1337 (0x45a090)
api_1     |     goexit: BYTE    $0x90   // NOP
api_1     | 
api_1     | [GIN] 2019/07/31 - 14:58:53 | 500 |    695.0698ms |      172.18.0.1 | POST     /api/post/image

A:

I set environment variable in docker-compose.yml and set value in console.
    environment:
      - AWS_ACCESS_KEY_ID
      - AWS_SECRET_ACCESS_KEY

$ export AWS_ACCESS_KEY_ID=$(aws --profile default configure get aws_access_key_id)
$ export AWS_SECRET_ACCESS_KEY=$(aws --profile default configure get aws_secret_access_key)

creds := credentials.NewStaticCredentials(os.Getenv("AWS_ACCESS_KEY_ID"), os.Getenv("AWS_SECRET_ACCESS_KEY"), "")

