Enable nilnesserr linter

.golangci.yml

@@ -19,6 +19,7 @@ linters:
     - gofmt             # Checks whether code was gofmt-ed
     - goheader          # Checks is file headers matche a given pattern
     - intrange          # Checking for loops that could use an integer range
+    - nilnesserr        # Reports constructs that check for err != nil but return a different nil value error
     - nolintlint        # Find ill-formed or insufficiently explained nolint directives
     - nosprintfhostport # Detects misuses of Sprintf to construct hosts with ports in a URL
     - perfsprint        # Checks for faster fmt.Sprintf alternatives

pkg/token/joindecode.go

@@ -39,12 +39,12 @@ func DecodeJoinToken(token string) ([]byte, error) {
 
 	var buf bytes.Buffer
 	_, err = io.Copy(&buf, gz)
-	gzErr := gz.Close()
+	closeErr := gz.Close()
 	if err != nil {
 		return nil, err
 	}
-	if gzErr != nil {
-		return nil, err
+	if closeErr != nil {
+		return nil, closeErr
 	}
 
 	return buf.Bytes(), nil