Add AWS_REGION env var to specify s3 region

internal/backend/s3/config.go

@@ -22,6 +22,7 @@ type Config struct {
 
 	Connections uint `option:"connections" help:"set a limit for the number of concurrent connections (default: 5)"`
 	MaxRetries  uint `option:"retries" help:"set the number of retries attempted"`
+	Region      string
 }
 
 // NewConfig returns a new Config with the default values filled in.

internal/backend/s3/s3.go

@@ -66,7 +66,7 @@ func open(cfg Config, rt http.RoundTripper) (*Backend, error) {
 			},
 		},
 	})
-	client, err := minio.NewWithCredentials(cfg.Endpoint, creds, !cfg.UseHTTP, "")
+	client, err := minio.NewWithCredentials(cfg.Endpoint, creds, !cfg.UseHTTP, cfg.Region)
 	if err != nil {
 		return nil, errors.Wrap(err, "minio.NewWithCredentials")
 	}