pkg/ranger: fix linting errors

pkg/ranger/common.go

@@ -7,4 +7,5 @@ import (
 	"github.com/zeebo/errs"
 )
 
+// Error is the errs class of standard Ranger errors
 var Error = errs.Class("ranger error")

pkg/ranger/content.go

@@ -175,10 +175,9 @@ func checkPreconditions(w http.ResponseWriter, r *http.Request,
 		if r.Method == "GET" || r.Method == "HEAD" {
 			writeNotModified(w)
 			return true, ""
-		} else {
-			w.WriteHeader(http.StatusPreconditionFailed)
-			return true, ""
 		}
+		w.WriteHeader(http.StatusPreconditionFailed)
+		return true, ""
 	case condNone:
 		if checkIfModifiedSince(r, modtime) == condFalse {
 			writeNotModified(w)
@@ -311,9 +310,8 @@ func checkIfRange(w http.ResponseWriter, r *http.Request, modtime time.Time) (
 	if etag != "" {
 		if etagStrongMatch(etag, w.Header().Get("Etag")) {
 			return condTrue
-		} else {
-			return condFalse
 		}
+		return condFalse
 	}
 	// The If-Range value is typically the ETag value, but it may also be
 	// the modtime date. See golang.org/issue/8367.

pkg/ranger/reader.go

@@ -32,8 +32,10 @@ func (f *fatalReader) Read(p []byte) (n int, err error) {
 // ByteRanger turns a byte slice into a Ranger
 type ByteRanger []byte
 
+// Size implements Ranger.Size
 func (b ByteRanger) Size() int64 { return int64(len(b)) }
 
+// Range implements Ranger.Range
 func (b ByteRanger) Range(offset, length int64) io.Reader {
 	if offset < 0 {
 		return FatalReader(Error.New("negative offset"))