cmd/protoc-gen-go: print version to stdout

Fixes #1279

Change-Id: I2f5459087c915cd1fc1e38ccbaa7c44b0f286137
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/301952
Trust: Joe Tsai <joetsai@digital-static.net>
Reviewed-by: Damien Neil <dneil@google.com>

cmd/protoc-gen-go/main.go

diff --git a/cmd/protoc-gen-go/main.go b/cmd/protoc-gen-go/main.go
index a354df9..d3187bb 100644
--- a/cmd/protoc-gen-go/main.go
+++ b/cmd/protoc-gen-go/main.go
@@ -23,7 +23,7 @@
 
 func main() {
 	if len(os.Args) == 2 && os.Args[1] == "--version" {
-		fmt.Fprintf(os.Stderr, "%v %v\n", filepath.Base(os.Args[0]), version.String())
+		fmt.Fprintf(os.Stdout, "%v %v\n", filepath.Base(os.Args[0]), version.String())
 		os.Exit(0)
 	}