all: fix golint violations

Change-Id: I35d9f6842ec2e9b36c14672a05c4381441bda87a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/224582
Reviewed-by: Herbie Ong <herbie@google.com>
diff --git a/internal/flags/flags.go b/internal/flags/flags.go
index ab62da2..58372dd 100644
--- a/internal/flags/flags.go
+++ b/internal/flags/flags.go
@@ -16,7 +16,7 @@
 // As such, functionality may suddenly be removed or changed at our discretion.
 const ProtoLegacy = protoLegacy
 
-// LazyUnmarshalExtension specifies whether to lazily unmarshal extensions.
+// LazyUnmarshalExtensions specifies whether to lazily unmarshal extensions.
 //
 // Lazy extension unmarshaling validates the contents of message-valued
 // extension fields at unmarshal time, but defers creating the message