Add more linters to improve code readability (#19989)

Add nakedret, unconvert, wastedassign, stylecheck and nolintlint linters to improve code readability

- nakedret - https://github.com/alexkohler/nakedret - nakedret is a Go static analysis tool to find naked returns in functions greater than a specified function length.
- unconvert - https://github.com/mdempsky/unconvert - Remove unnecessary type conversions
- wastedassign - https://github.com/sanposhiho/wastedassign -  wastedassign finds wasted assignment statements.
- notlintlint -  Reports ill-formed or insufficient nolint directives
- stylecheck - https://staticcheck.io/docs/checks/#ST - keep style consistent
  - excluded: [ST1003 - Poorly chosen identifier](https://staticcheck.io/docs/checks/#ST1003) and [ST1005 - Incorrectly formatted error string](https://staticcheck.io/docs/checks/#ST1005)

modules/timeutil/since.go

@@ -30,7 +30,7 @@ func round(s float64) int64 {
 }
 
 func computeTimeDiffFloor(diff int64, lang string) (int64, string) {
-	diffStr := ""
+	var diffStr string
 	switch {
 	case diff <= 0:
 		diff = 0
@@ -88,7 +88,7 @@ func computeTimeDiffFloor(diff int64, lang string) (int64, string) {
 }
 
 func computeTimeDiff(diff int64, lang string) (int64, string) {
-	diffStr := ""
+	var diffStr string
 	switch {
 	case diff <= 0:
 		diff = 0

modules/timeutil/timestamp.go

@@ -57,7 +57,7 @@ func (ts TimeStamp) AsTime() (tm time.Time) {
 // AsTimeInLocation convert timestamp as time.Time in Local locale
 func (ts TimeStamp) AsTimeInLocation(loc *time.Location) (tm time.Time) {
 	tm = time.Unix(int64(ts), 0).In(loc)
-	return
+	return tm
 }
 
 // AsTimePtr convert timestamp as *time.Time in Local locale