move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/tdsync/supervisor.go

@@ -0,0 +1,64 @@
+package tdsync
+
+import (
+	"context"
+	"sync"
+)
+
+// Supervisor is simple task group primitive to control multiple
+// long-live tasks.
+// Unlike Groups, Supervisor does not cancel when one task is failed.
+// Unlike WaitGroup and errgroup.Group this is not allowed to use zero value.
+type Supervisor struct {
+	wg sync.WaitGroup
+
+	ctx    context.Context
+	cancel context.CancelFunc
+
+	onError func(err error)
+}
+
+// NewSupervisor creates new Supervisor.
+func NewSupervisor(parent context.Context) *Supervisor {
+	ctx, cancel := context.WithCancel(parent)
+
+	return &Supervisor{
+		ctx:    ctx,
+		cancel: cancel,
+	}
+}
+
+// WithErrorHandler sets tasks error handler
+// Must be called before any Go calls.
+func (s *Supervisor) WithErrorHandler(h func(err error)) *Supervisor {
+	s.onError = h
+	return s
+}
+
+// Go calls the given function in a new goroutine.
+func (s *Supervisor) Go(task func(ctx context.Context) error) {
+	s.wg.Add(1)
+	go func() {
+		defer s.wg.Done()
+
+		if err := task(s.ctx); err != nil {
+			if s.onError != nil {
+				s.onError(err)
+			}
+		}
+	}()
+}
+
+// Cancel cancels all goroutines in group.
+//
+// Note: context cancellation error can be returned by Wait().
+func (s *Supervisor) Cancel() {
+	s.cancel()
+}
+
+// Wait blocks until all function calls from the Go method have returned, then
+// returns the first non-nil error (if any) from them.
+func (s *Supervisor) Wait() error {
+	s.wg.Wait()
+	return nil
+}