fix gopath compatible with windows

tool/kratos-protoc/protoc.go

@@ -144,7 +144,15 @@ func latestKratos() (string, error) {
 }
 
 func gopath() (gp string) {
-	gopaths := strings.Split(os.Getenv("GOPATH"), ":")
+	var gopaths []string
+
+	switch runtime.GOOS {
+	case "windows":
+		gopaths = strings.Split(os.Getenv("GOPATH"), ";")
+	default:
+		gopaths = strings.Split(os.Getenv("GOPATH"), ":")
+	}
+
 	if len(gopaths) == 1 && gopaths[0] != "" {
 		return gopaths[0]
 	}