add util/errgroup.go to collect all errors

Author: defbin

pbm/util/errgroup.go

@@ -0,0 +1,44 @@
+package util
+
+import (
+	"runtime"
+	"sync"
+)
+
+type errorGroup struct {
+	errs []error
+	mu   sync.Mutex
+
+	wg  sync.WaitGroup
+	sem chan struct{}
+}
+
+func NewErrorGroup(limit int) *errorGroup {
+	if limit <= 0 {
+		limit = runtime.NumCPU()
+	}
+	return &errorGroup{sem: make(chan struct{}, limit)}
+}
+
+func (g *errorGroup) Wait() []error {
+	g.wg.Wait()
+	return g.errs
+}
+
+func (g *errorGroup) Go(f func() error) {
+	g.wg.Add(1)
+	go func() {
+		g.sem <- struct{}{}
+
+		defer func() {
+			<-g.sem
+			g.wg.Done()
+		}()
+
+		if err := f(); err != nil {
+			g.mu.Lock()
+			g.errs = append(g.errs, err)
+			g.mu.Unlock()
+		}
+	}()
+}