encoding/protobuf: fix linter issues

Change-Id: I3c434b7e7b1213d91404044b6bffae36d0b7bcbe
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/2725
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/encoding/protobuf/parse.go b/encoding/protobuf/parse.go
index 48617c9..7f36f7f 100644
--- a/encoding/protobuf/parse.go
+++ b/encoding/protobuf/parse.go
@@ -187,13 +187,6 @@
 	pkg   *protoConverter
 }
 
-type pkgInfo struct {
-	importPath string // the import path
-	goPath     string // The Go import path
-	shortName  string // Used for the cue package path, default is base of goPath
-	protoName  string // the protobuf package name
-}
-
 func (p *protoConverter) toCUEPos(pos scanner.Position) token.Pos {
 	return p.tfile.Pos(pos.Offset, 0)
 }
@@ -277,8 +270,7 @@
 	}
 	for i := len(p.scope) - 1; i > 0; i-- {
 		if m, ok := p.scope[i][name]; ok {
-			cueName := m.ref
-			cueName = strings.Replace(m.ref, ".", "_", -1)
+			cueName := strings.Replace(m.ref, ".", "_", -1)
 			return cueName
 		}
 	}
diff --git a/encoding/protobuf/protobuf.go b/encoding/protobuf/protobuf.go
index d1cdad0..9ae5b64 100644
--- a/encoding/protobuf/protobuf.go
+++ b/encoding/protobuf/protobuf.go
@@ -116,7 +116,6 @@
 	paths  []string
 
 	fileCache map[string]result
-	instCache map[string]*build.Instance
 	imports   map[string]*build.Instance
 
 	errs errors.Error
diff --git a/encoding/protobuf/protobuf_test.go b/encoding/protobuf/protobuf_test.go
index fb0fe69..d62951d 100644
--- a/encoding/protobuf/protobuf_test.go
+++ b/encoding/protobuf/protobuf_test.go
@@ -56,7 +56,7 @@
 
 			wantFile := filepath.Join("testdata", filepath.Base(file)+".out.cue")
 			if *update {
-				ioutil.WriteFile(wantFile, out.Bytes(), 0644)
+				_ = ioutil.WriteFile(wantFile, out.Bytes(), 0644)
 				return
 			}
 
@@ -85,10 +85,10 @@
 	}
 
 	b := NewExtractor(c)
-	b.AddFile("networking/v1alpha3/gateway.proto", nil)
-	b.AddFile("mixer/v1/attributes.proto", nil)
-	b.AddFile("mixer/v1/mixer.proto", nil)
-	b.AddFile("mixer/v1/config/client/client_config.proto", nil)
+	_ = b.AddFile("networking/v1alpha3/gateway.proto", nil)
+	_ = b.AddFile("mixer/v1/attributes.proto", nil)
+	_ = b.AddFile("mixer/v1/mixer.proto", nil)
+	_ = b.AddFile("mixer/v1/config/client/client_config.proto", nil)
 
 	files, err := b.Files()
 	if err != nil {