fix: prevent race condition in concurrent task execution

go.mod

@@ -0,0 +1,3 @@
+module github.com/mmccl5/go-task-task
+
+go 1.22.5

workspace/task/runner.go

@@ -7,8 +7,9 @@ import (
 )
 
 type Runner struct {
-	mu    sync.RWMutex
-	tasks []*Task
+	mu      sync.RWMutex
+	tasks   []*Task
+	running bool
 }
 
 func NewRunner() *Runner {
@@ -24,10 +25,21 @@ func (r *Runner) AddTask(t *Task) {
 }
 
 func (r *Runner) Run(ctx context.Context) {
-	r.mu.RLock()
+	r.mu.Lock()
+	if r.running {
+		r.mu.Unlock()
+		return
+	}
+	r.running = true
 	tasks := make([]*Task, len(r.tasks))
 	copy(tasks, r.tasks)
-	r.mu.RUnlock()
+	r.mu.Unlock()
+
+	defer func() {
+		r.mu.Lock()
+		r.running = false
+		r.mu.Unlock()
+	}()
 
 	var wg sync.WaitGroup
 	for _, t := range tasks {
@@ -36,34 +48,30 @@ func (r *Runner) Run(ctx context.Context) {
 			defer wg.Done()
 
 			if ctx.Err() != nil {
-				task.mu.Lock()
-				task.State = StateFailed
-				task.Err = ctx.Err()
-				task.History = append(task.History, StateFailed)
-				task.mu.Unlock()
+				task.SetState(StateFailed)
+				task.SetErr(ctx.Err())
 				return
 			}
 
+			task.SetState(StateRunning)
+
 			task.mu.Lock()
-			task.State = StateRunning
 			task.StartedAt = time.Now()
-			task.History = append(task.History, StateRunning)
 			task.mu.Unlock()
 
 			err := task.Action(ctx)
 
 			task.mu.Lock()
 			task.FinishedAt = time.Now()
+			task.mu.Unlock()
+
 			if err != nil {
-				task.State = StateFailed
-				task.Err = err
-				task.History = append(task.History, StateFailed)
+				task.SetState(StateFailed)
+				task.SetErr(err)
 			} else {
-				task.State = StateCompleted
-				task.History = append(task.History, StateCompleted)
+				task.SetState(StateCompleted)
 			}
-			task.mu.Unlock()
 		}(t)
 	}
 	wg.Wait()
-}
+}