[alerts-dispatcher] update to build again :) also fixes a concurrent map access

go/src/infra/monitoring/looper/looper.go

Index: go/src/infra/monitoring/looper/looper.go
diff --git a/go/src/infra/monitoring/looper/looper.go b/go/src/infra/monitoring/looper/looper.go
index 9bbea5c94061a8a4c3385461da09b1b57b7b5893..2e3c3324961cf96bbb62c34c18ab706776812a68 100644
--- a/go/src/infra/monitoring/looper/looper.go
+++ b/go/src/infra/monitoring/looper/looper.go
@@ -69,7 +69,9 @@ func Run(ctx context.Context, f Runner, cycle time.Duration, maxErrs int, c cloc
 		}
 
 		nextCycle = cycle - dur
-		tmr.Reset(nextCycle)
+		if tmr.Reset(nextCycle) {
+			log.Errorf("Timer was still active")
+		}
 	}
 
 	// Run f at least once.
@@ -77,12 +79,15 @@ func Run(ctx context.Context, f Runner, cycle time.Duration, maxErrs int, c cloc
 
 	// Keep running f until ctx is done.
 	for {
-		if ar := <-tmr.GetC(); ar.Incomplete() {
-			return ret
-		}
-		run()
-		if !ret.Success {
+		select {
+		case <-ctx.Done():
+			tmr.Stop()
 			return ret
+		case <-tmr.GetC():
+			run()
+			if !ret.Success {
+				return ret
+			}
 		}
 	}
 }