add http operation const (#2086)

cmd/protoc-gen-go-http/template.go

@@ -9,6 +9,11 @@ import (
 var httpTemplate = `
 {{$svrType := .ServiceType}}
 {{$svrName := .ServiceName}}
+
+{{- range .Methods}}
+const Operation{{.OriginalName}} = "/{{$svrName}}/{{.OriginalName}}"
+{{- end}}
+
 type {{.ServiceType}}HTTPServer interface {
 {{- range .MethodSets}}
 	{{.Name}}(context.Context, *{{.Request}}) (*{{.Reply}}, error)
@@ -46,7 +51,7 @@ func _{{$svrType}}_{{.Name}}{{.Num}}_HTTP_Handler(srv {{$svrType}}HTTPServer) fu
 			return err
 		}
 		{{- end}}
-		http.SetOperation(ctx,"/{{$svrName}}/{{.OriginalName}}")
+		http.SetOperation(ctx,Operation{{.OriginalName}})
 		h := ctx.Middleware(func(ctx context.Context, req interface{}) (interface{}, error) {
 			return srv.{{.Name}}(ctx, req.(*{{.Request}}))
 		})
@@ -79,7 +84,7 @@ func (c *{{$svrType}}HTTPClientImpl) {{.Name}}(ctx context.Context, in *{{.Reque
 	var out {{.Reply}}
 	pattern := "{{.Path}}"
 	path := binding.EncodeURL(pattern, in, {{not .HasBody}})
-	opts = append(opts, http.Operation("/{{$svrName}}/{{.OriginalName}}"))
+	opts = append(opts, http.Operation(Operation{{.OriginalName}}))
 	opts = append(opts, http.PathTemplate(pattern))
 	{{if .HasBody -}}
 	err := c.cc.Invoke(ctx, "{{.Method}}", path, in{{.Body}}, &out{{.ResponseBody}}, opts...)