fix: use atomic for ids (#634)

closes #622

Signed-off-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>
Co-authored-by: Ville Valkonen <weezel@users.noreply.github.com>

timer/timer.go

@@ -2,22 +2,16 @@
 package timer
 
 import (
-	"sync"
+	"sync/atomic"
 	"time"
 
 	tea "github.com/charmbracelet/bubbletea"
 )
 
-var (
-	lastID int
-	idMtx  sync.Mutex
-)
+var lastID int64
 
 func nextID() int {
-	idMtx.Lock()
-	defer idMtx.Unlock()
-	lastID++
-	return lastID
+	return int(atomic.AddInt64(&lastID, 1))
 }
 
 // Authors note with regard to start and stop commands: