golang改进errGroup，实现并发超时控制

需求

在并发控制中，想实现以下功能

1、并发超时控制

2、一个出错，主程序退出

3、兼容errGroup

然后对errGroup进行一次改写

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package utils   import (     "context"     "errors"     "fmt"     "sync"     "time" )   type token struct{}   // A Group is a collection of goroutines working on subtasks that are part of // the same overall task. // // A zero Group is valid, has no limit on the number of active goroutines, // and does not cancel on error. type Group struct {     cancel func()       wg sync.WaitGroup       sem chan token       errOnce sync.Once     err     error     unsafe  bool     ctx     context.Context }   var errTimeout = errors.New("超时了")   func (g *Group) done() {     if g.sem != nil {         <-g.sem     }     g.wg.Done() }   // WithContext returns a new Group and an associated Context derived from ctx. // // The derived Context is canceled the first time a function passed to Go // returns a non-nil error or the first time Wait returns, whichever occurs // first. func WithContext(ctx context.Context) (*Group, context.Context) {     ctx, cancel := context.WithCancel(ctx)     return &Group{cancel: cancel, unsafe: true, ctx: ctx}, ctx }   // GroupTimeoutContext 超时设置 func GroupTimeoutContext(parent context.Context, timeout time.Duration) (*Group, context.Context) {     ctx, cancel := context.WithTimeout(parent, timeout)     return &Group{cancel: cancel, unsafe: true, ctx: ctx}, ctx }   // 超时设置 func GroupTimeout(parent context.Context, timeout time.Duration) *Group {     ctx, cancel := context.WithTimeout(parent, timeout)     return &Group{cancel: cancel, unsafe: true, ctx: ctx} }   // UnsafeGroup 获取不安全的同步锁（出错就退出） func UnsafeGroup() *Group {     var g Group     g.unsafe = true     g.ctx, g.cancel = context.WithCancel(context.Background())     return &g }   // Wait blocks until all function calls from the Go method have returned, then // returns the first non-nil error (if any) from them. func (g *Group) Wait() error {     if g.unsafe {         monitor := make(chan struct{})         go func() {             g.wg.Wait()             close(monitor)         }()         select {         case <-g.ctx.Done():             g.errOnce.Do(func() {                 if nil == g.err {                     g.err = errTimeout                 }             })         case <-monitor:         }     } else {         g.wg.Wait()     }       if g.cancel != nil {         g.cancel()     }     return g.err }   // Go calls the given function in a new goroutine. // It blocks until the new goroutine can be added without the number of // active goroutines in the group exceeding the configured limit. // // The first call to return a non-nil error cancels the group; its error will be // returned by Wait. func (g *Group) Go(f func() (err error)) {     if g.sem != nil {         g.sem <- token{}     }     if g.unsafe && g.cancel == nil {         g.ctx, g.cancel = context.WithCancel(context.Background())     }     g.wg.Add(1)       go func() {         defer g.done()         if err := f(); err != nil {             g.errOnce.Do(func() {                 if nil == g.err {                     g.err = err                 }                 if g.cancel != nil {                     g.cancel()                 }             })         }     }() }   // TryGo calls the given function in a new goroutine only if the number of // active goroutines in the group is currently below the configured limit. // // The return value reports whether the goroutine was started. func (g *Group) TryGo(f func() error) bool {     if g.sem != nil {         select {         case g.sem <- token{}:             // Note: this allows barging iff channels in general allow barging.         default:             return false         }     }       if g.unsafe && g.cancel == nil {         g.ctx, g.cancel = context.WithCancel(context.Background())     }       g.wg.Add(1)     go func() {         defer g.done()           if err := f(); err != nil {             g.errOnce.Do(func() {                 if nil == g.err {                     g.err = err                 }                 if g.cancel != nil {                     g.cancel()                 }             })         }     }()     return true }   // SetLimit limits the number of active goroutines in this group to at most n. // A negative value indicates no limit. // // Any subsequent call to the Go method will block until it can add an active // goroutine without exceeding the configured limit. // // The limit must not be modified while any goroutines in the group are active. func (g *Group) SetLimit(n int) {     if n < 0 {         g.sem = nil         return     }     if len(g.sem) != 0 {         panic(fmt.Errorf("errgroup: modify limit while %v goroutines in the group are still active", len(g.sem)))     }     g.sem = make(chan token, n) }   // IsErr 判断是否执行出错 func (g *Group) IsErr(err error, message ...interface{}) bool {     // 有错误直接返回     if g.err != nil {         return true     }     // 无错误直接返回     if err == nil {         return false     }     switch len(message) {     case 0:         g.errOnce.Do(func() {             if nil == g.err {                 g.err = err             }             if g.cancel != nil {                 g.cancel()             }         })     case 1:         g.errOnce.Do(func() {             if nil == g.err {                 g.err = fmt.Errorf("%v:%w", message[0], err)             }             if g.cancel != nil {                 g.cancel()             }         })     default:         // 格式化输出         g.errOnce.Do(func() {             if nil == g.err {                 s, _ := message[0].(string)                 g.err = fmt.Errorf("%s:%w", fmt.Sprintf(s, message[1:]...), err)             }             if g.cancel != nil {                 g.cancel()             }         })     }     return true }   func IsTimeout(err error) bool {     if err == nil {         return false     }     return errors.Is(err, errTimeout) }