func (e *EnvMinio) Retrieve() (Value, error) {
	e.retrieved = false
	id := os.Getenv("MINIO_ACCESS_KEY")
	secret := os.Getenv("MINIO_SECRET_KEY")
	signerType := SignatureV4
	if id == "" || secret == "" {
		signerType = SignatureAnonymous
	}
	e.retrieved = true
	return Value{
		AccessKeyID:     id,
		SecretAccessKey: secret,
		SignerType:      signerType,
	}, nil
}
Retrieve retrieves the keys from the environment.
package credentials
import "os"
type EnvMinio struct {
	retrieved bool
}
func NewEnvMinio() *Credentials {
	return New(&EnvMinio{})
}