// Copyright 2023 The Gitea Authors. All rights reserved.// SPDX-License-Identifier: MIT package queue import (	"context"	"time") const (	backoffBegin = 50 * time.Millisecond	backoffUpper = 2 * time.Second) type (	backoffFuncRetErr[T any] func() (retry bool, ret T, err error)	backoffFuncErr           func() (retry bool, err error)) func backoffRetErr[T any](ctx context.Context, begin, upper time.Duration, end <-chan time.Time, fn backoffFuncRetErr[T]) (ret T, err error) {	d := begin	for {		// check whether the context has been cancelled or has reached the deadline, return early		select {		case <-ctx.Done():			return ret, ctx.Err()		case <-end:			return ret, context.DeadlineExceeded		default:		} 		// call the target function		retry, ret, err := fn()		if err != nil {			return ret, err		}		if !retry {			return ret, nil		} 		// wait for a while before retrying, and also respect the context & deadline		select {		case <-ctx.Done():			return ret, ctx.Err()		case <-time.After(d):			d *= 2			if d > upper {				d = upper			}		case <-end:			return ret, context.DeadlineExceeded		}	}} func backoffErr(ctx context.Context, begin, upper time.Duration, end <-chan time.Time, fn backoffFuncErr) error {	_, err := backoffRetErr(ctx, begin, upper, end, func() (retry bool, ret any, err error) {		retry, err = fn()		return retry, nil, err	})	return err}