func GetGopherJSPackage(file *descriptor.FileDescriptorProto) string {
	if file == nil || file.Options == nil {
		return ""
	}
	e, err := proto.GetExtension(file.Options, E_GopherjsPackage)
	if err != nil {
		return ""
	}
	if s, ok := e.(*string); ok {
		return *s
	}
	return ""
}
GetGopherJSPackage returns the (gopherjs.gopherjs_package) option if
specified, or an empty string if it was not.
package gopherjs
import (
	"github.com/golang/protobuf/proto"
	"github.com/golang/protobuf/protoc-gen-go/descriptor"
)