package singledo import ( "sync" "time" ) type call[T any] struct { wg sync.WaitGroup val T err error } type Single[T any] struct { mux sync.Mutex last time.Time wait time.Duration call *call[T] result *Result[T] } type Result[T any] struct { Val T Err error } // Do single.Do likes sync.singleFlight //lint:ignore ST1008 it likes sync.singleFlight func (s *Single[T]) Do(fn func() (T, error)) (v T, err error, shared bool) { s.mux.Lock() now := time.Now() if now.Before(s.last.Add(s.wait)) { s.mux.Unlock() return s.result.Val, s.result.Err, true } if callM := s.call; callM != nil { s.mux.Unlock() callM.wg.Wait() return callM.val, callM.err, true } callM := &call[T]{} callM.wg.Add(1) s.call = callM s.mux.Unlock() callM.val, callM.err = fn() callM.wg.Done() s.mux.Lock() s.call = nil s.result = &Result[T]{callM.val, callM.err} s.last = now s.mux.Unlock() return callM.val, callM.err, false } func (s *Single[T]) Reset() { s.last = time.Time{} } func NewSingle[T any](wait time.Duration) *Single[T] { return &Single[T]{wait: wait} }