signer

type NopSigner struct{}

type Signer interface {
	Sign(ctx context.Context, signingCtx *SigningContext) error
	Presign(ctx context.Context, signingCtx *SigningContext) error
}

type SignerV1 struct {
}

type SigningContext struct {
	//input
	Product string
	Region  string
	Bucket  string
	Key     string
	Request *http.Request

	SubResource []string

	// output
	Credentials   *credentials.Credentials
	Time          time.Time
	SignedHeaders http.Header
	StringToSign  string
}