Self-hosted S3.
Single binary. Zero dependencies.

import boto3

s3 = boto3.client("s3",
    endpoint_url="http://localhost:9000",
    aws_access_key_id="AKIAIOSFODNN7EXAMPLE",
    aws_secret_access_key="wJalrXUtnFEMI/K7MDENG",
)

# Upload
s3.upload_file("photo.jpg", "photos", "photo.jpg")

# Download
s3.download_file("photos", "photo.jpg", "download.jpg")

# List objects
for obj in s3.list_objects_v2(Bucket="photos")["Contents"]:
    print(obj["Key"], obj["Size"])

package main

import (
    "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"
)

func main() {
    sess := session.Must(session.NewSession(&aws.Config{
        Endpoint:         aws.String("http://localhost:9000"),
        Region:           aws.String("us-east-1"),
        Credentials:      credentials.NewStaticCredentials("AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG", ""),
        S3ForcePathStyle: aws.Bool(true),
    }))

    svc := s3.New(sess)

    // List buckets
    result, _ := svc.ListBuckets(nil)
    for _, b := range result.Buckets {
        fmt.Println(*b.Name)
    }
}