From 2e2d8c483d75402ebfc50b286494d72d2bf3bdd8 Mon Sep 17 00:00:00 2001
From: comicrime <molodoy.p4elovek@yandex.ru>
Date: Mon, 7 Sep 2026 00:05:00 +0300
Subject: [PATCH 1/2] + safegroup

---
 safegroup/go.mod       |   3 ++
 safegroup/safegroup.go | 109 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 112 insertions(+)
 create mode 100644 safegroup/go.mod
 create mode 100644 safegroup/safegroup.go

diff --git a/safegroup/go.mod b/safegroup/go.mod
new file mode 100644
index 0000000..4f40baa
--- /dev/null
+++ b/safegroup/go.mod
@@ -0,0 +1,3 @@
+module github.com/draincloud/callpack/safegroup
+
+go 1.26.3
diff --git a/safegroup/safegroup.go b/safegroup/safegroup.go
new file mode 100644
index 0000000..850ad91
--- /dev/null
+++ b/safegroup/safegroup.go
@@ -0,0 +1,109 @@
+package safegroup
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+)
+
+var ErrPanic = errors.New("panic in a goroutine")
+
+type SafeGroup struct {
+	cancel func(error)
+
+	wg sync.WaitGroup
+
+	sem chan token
+
+	errOnce sync.Once
+	err     error
+}
+
+type token struct{}
+
+func (g *SafeGroup) done() {
+	r := recover()
+	if r != nil {
+		g.errOnce.Do(func() {
+			g.err = fmt.Errorf("safegroup: %w: %s", ErrPanic, r)
+			if g.cancel != nil {
+				g.cancel(g.err)
+			}
+		})
+	}
+
+	if g.sem != nil {
+		<-g.sem
+	}
+	g.wg.Done()
+}
+
+func WithContext(ctx context.Context) (*SafeGroup, context.Context) {
+	ctx, cancel := context.WithCancelCause(ctx)
+	return &SafeGroup{cancel: cancel}, ctx
+}
+
+func (g *SafeGroup) Wait() error {
+	g.wg.Wait()
+	if g.cancel != nil {
+		g.cancel(g.err)
+	}
+	return g.err
+}
+
+func (g *SafeGroup) Go(f func() error) {
+	if g.sem != nil {
+		g.sem <- token{}
+	}
+
+	g.wg.Add(1)
+	go func() {
+		defer g.done()
+
+		if err := f(); err != nil {
+			g.errOnce.Do(func() {
+				g.err = err
+				if g.cancel != nil {
+					g.cancel(g.err)
+				}
+			})
+		}
+	}()
+}
+
+func (g *SafeGroup) TryGo(f func() error) bool {
+	if g.sem != nil {
+		select {
+		case g.sem <- token{}:
+		default:
+			return false
+		}
+	}
+
+	g.wg.Add(1)
+	go func() {
+		defer g.done()
+
+		if err := f(); err != nil {
+			g.errOnce.Do(func() {
+				g.err = err
+				if g.cancel != nil {
+					g.cancel(g.err)
+				}
+			})
+		}
+	}()
+	return true
+}
+
+func (g *SafeGroup) SetLimit(n int) {
+	if n < 0 {
+		g.sem = nil
+		return
+	}
+	if active := len(g.sem); active != 0 {
+		panic(fmt.Errorf("safegroup: modify limit while %v goroutines in the group are still active", active))
+	}
+	g.sem = make(chan token, n)
+}

From e8a5fc0f510fc2846e18084b260a395cd6c7c022 Mon Sep 17 00:00:00 2001
From: comicrime <molodoy.p4elovek@yandex.ru>
Date: Mon, 7 Sep 2026 00:11:30 +0300
Subject: [PATCH 2/2] +1

---
 safegroup/go.sum | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 safegroup/go.sum

diff --git a/safegroup/go.sum b/safegroup/go.sum
new file mode 100644
index 0000000..e69de29