examples/panic: Make an example to show off aforementioned feature

examples/panic/main.go

@@ -0,0 +1,35 @@
+// Example panic demonstrates how the environment can restart actors if they
+// fail.
+package main
+
+import "log"
+import "time"
+import "errors"
+import "context"
+import "math/rand"
+import "git.tebibyte.media/sashakoshka/camfish"
+
+func main() {
+	camfish.Run("panic",
+		"Example panic demonstrates how the environment can restart " +
+		"actors if they fail",
+		new(actor))
+}
+
+// actor is an incorrectly implemented actor that panics and errs randomly.
+type actor struct { }
+var _ camfish.Runnable = new(actor)
+func (this *actor) Type() string { return "panic" }
+
+func (this *actor) Run(ctx context.Context) error {
+	log.Println("(i) [panic] panicking in 10 seconds")
+	select {
+	case <- ctx.Done(): return ctx.Err()
+	case <- time.After(time.Second * 10):
+		if rand.Int() % 2 == 0 {
+			panic("this is a panic")
+		} else {
+			return errors.New("this is an error")
+		}
+	}
+}

util.go

@@ -12,6 +12,19 @@ import "strings"
 import "context"
 import "sync/atomic"
 import "unicode/utf8"
+import "runtime/debug"
+
+func panicErr(message any, stack []byte) (err error) {
+	if panErr, ok := message.(error); ok {
+		err = panErr
+	} else {
+		err = errors.New(fmt.Sprint(message))
+	}
+	if stack != nil {
+		err = fmt.Errorf("%w: %s", err, stack)
+	}
+	return err
+}
 
 func defaul[T comparable](value, def T) T {
 	var zero T
@@ -22,11 +35,7 @@ func defaul[T comparable](value, def T) T {
 func panicWrap(f func() error) (err error) {
 	defer func () {
 		if pan := recover(); pan != nil {
-			if panErr, ok := pan.(error); ok {
+			err = panicErr(pan, debug.Stack())
-				err = panErr
-			} else {
-				err = errors.New(fmt.Sprint(pan))
-			}
 		}
 	} ()
 	
@@ -37,11 +46,7 @@ func panicWrap(f func() error) (err error) {
 func panicWrapCtx(ctx context.Context, f func(context.Context) error) (err error) {
 	defer func () {
 		if pan := recover(); pan != nil {
-			if panErr, ok := pan.(error); ok {
+			err = panicErr(pan, debug.Stack())
-				err = panErr
-			} else {
-				err = errors.New(fmt.Sprint(pan))
-			}
 		}
 	} ()