Expanded linting + fix warnings (#1396)

* Expand the linters and types of warnings to improve consistency and safety

* Fail lint workflow if there are errors

* golint has been replaced by revive

* Hand-pick some of the default exclude list

* Ignore error when trying to delete preview gif

* Ignore linter warning opening playlist path

* Rename user field Id -> ID

* A bunch of renames to address linter warnings

* Rename ChatClient -> Client per linter suggestion best practice

* Rename ChatServer -> Server per linter suggestion best practice

* More linter warning fixes

* Add missing comments to all exported functions and properties

core/transcoder/thumbnailGenerator.go

@@ -18,6 +18,7 @@ import (
 
 var _timer *time.Ticker
 
+// StopThumbnailGenerator will stop the periodic generating of a thumbnail from video.
 func StopThumbnailGenerator() {
 	if _timer != nil {
 		_timer.Stop()
@@ -98,11 +99,11 @@ func fireThumbnailGenerator(segmentPath string, variantIndex int) error {
 	ffmpegCmd := strings.Join(thumbnailCmdFlags, " ")
 	if _, err := exec.Command("sh", "-c", ffmpegCmd).Output(); err != nil {
 		return err
-	} else {
-		// rename temp file
-		if err := os.Rename(outputFileTemp, outputFile); err != nil {
-			log.Errorln(err)
-		}
+	}
+
+	// rename temp file
+	if err := os.Rename(outputFileTemp, outputFile); err != nil {
+		log.Errorln(err)
 	}
 
 	// If YP support is enabled also create an animated GIF preview