feat: add WithoutCancel

ctxmeta/without_cancel.go

@@ -10,11 +10,11 @@ type asyncContext struct {
 }
 
 func (a asyncContext) Deadline() (deadline time.Time, ok bool) {
-	return time.Time{}, false
+	return
 }
 
 func (a asyncContext) Done() <-chan struct{} {
-	return make(chan struct{})
+	return nil
 }
 
 func (a asyncContext) Err() error {
@@ -28,11 +28,16 @@ func (a asyncContext) Value(key interface{}) interface{} {
 // WithoutCancel creates a new context from an existing context and inherits all
 // values from the existing context. However if the existing context is
 // cancelled, timeouts or passes deadline, the returning context will not be
-// affected. This is useful in an async HTTP handler. When the http response is sent, the request context will be cancelled. If you still want to access the value from request context (eg. tracing), you can use:
+// affected. This is useful in an async HTTP handler. When the http response is sent,
+// the request context will be cancelled. If you still want to access the value from request context (eg. tracing),
+// you can use:
 //  func(request *http.Request, responseWriter http.ResponseWriter) {
 //    go DoSomeSlowDatabaseOperation(WithoutCancel(request.Context()))
 //	  responseWriter.Write([]byte("ok"))
 //  }
 func WithoutCancel(requestScopeContext context.Context) (valueOnlyContext context.Context) {
+	if requestScopeContext == nil {
+		panic("cannot create context from nil parent")
+	}
 	return asyncContext{requestScopeContext}
 }

ctxmeta/without_cancel_test.go

@@ -24,3 +24,10 @@ func TestWithoutCancel(t *testing.T) {
 	assert.Nil(t, WithoutCancel(ctx).Err())
 	assert.Equal(t, "value", WithoutCancel(ctx).Value(key))
 }
+
+func TestWithoutCancel_Nil(t *testing.T) {
+	defer func() {
+		assert.Equal(t, recover(), "cannot create context from nil parent")
+	}()
+	WithoutCancel(nil)
+}