Fixed lint issues and missing documentation

internal/fetcher/worker_sleeper.go

@@ -11,7 +11,8 @@ import (
 // sleepDuration is how long the sleeper's simulated work takes.
 const sleepDuration = 60 * time.Second
 
-// Test source that just sleeps for 60 seconds to simulate doing work
+// runSleeper runs the sleeper test source until ctx is cancelled: every
+// configured interval it simulates work by sleeping for sleepDuration.
 func runSleeper(
 	ctx context.Context, conf *config.JobSearchConfig, since time.Time,
 ) error {