fix cmd proto server (#1098)

cmd/kratos/internal/proto/server/template.go

@@ -6,33 +6,40 @@ import (
 )
 
 var serviceTemplate = `
+{{- /* delete empty line */ -}}
 package service
 
-import(
+import (
-	"context"
+    "context"
 
-	pb "{{.Package}}"
+    pb "{{ .Package }}"
+    {{- if .GoogleEmpty }}
+    "google.golang.org/protobuf/types/known/emptypb"
+    {{- end }}
 )
 
-type {{.Service}}Service struct {
+type {{ .Service }}Service struct {
-	pb.Unimplemented{{.Service}}Server
+	pb.Unimplemented{{ .Service }}Server
 }
 
-func New{{.Service}}Service() *{{.Service}}Service {
+func New{{ .Service }}Service() *{{ .Service }}Service {
-	return &{{.Service}}Service{}
+	return &{{ .Service }}Service{}
 }
+
+{{- $s1 := "google.protobuf.Empty" }}
 {{ range .Methods }}
-func (s *{{.Service}}Service) {{.Name}}(ctx context.Context, req *pb.{{.Request}}) (*pb.{{.Reply}}, error) {
+func (s *{{ .Service }}Service) {{ .Name }}(ctx context.Context, req {{ if eq .Reply $s1 }}*emptypb.Empty{{ else }}*pb.{{ .Request }}{{ end }}) ({{ if eq .Reply $s1 }}*emptypb.Empty{{ else }}*pb.{{ .Reply }}{{ end }}, error) {
-	return &pb.{{.Reply}}{}, nil
+	return {{ if eq .Reply $s1 }}&emptypb.Empty{}{{ else }}&pb.{{ .Reply }}{}{{ end }}, nil
 }
 {{- end }}
 `
 
 // Service is a proto service.
 type Service struct {
-	Package string
+	Package     string
-	Service string
+	Service     string
-	Methods []*Method
+	Methods     []*Method
+	GoogleEmpty bool
 }
 
 // Method is a proto method.
@@ -45,6 +52,11 @@ type Method struct {
 
 func (s *Service) execute() ([]byte, error) {
 	buf := new(bytes.Buffer)
+	for _, method := range s.Methods {
+		if method.Request == "google.protobuf.Empty" {
+			s.GoogleEmpty = true
+		}
+	}
 	tmpl, err := template.New("service").Parse(serviceTemplate)
 	if err != nil {
 		return nil, err