change invoke handler directly to bytes buffer

core/resource.go

@@ -191,38 +191,17 @@ func (r *Resource) Invoke(ctx context.Context, symbol string, in io.Reader) (str
 	}
 	defer r.closeDescriptor()
 
-	// because of grpcurl directly fmt.Printf on their invoke function
-	// so we stub the Stdout using os.Pipe
-	backUpStdout := os.Stdout
-	defer func() {
-		os.Stdout = backUpStdout
-	}()
-
-	f, w, err := os.Pipe()
-	if err != nil {
-		return "", 0, err
-	}
-	os.Stdout = w
-
-	// copy the output in a separate goroutine so printing can't block indefinitely
-	outC := make(chan string, 1)
-	var buf bytes.Buffer
-	go func() {
-		io.Copy(&buf, f)
-		outC <- buf.String()
-		f.Close()
-	}()
+	var resultBuffer bytes.Buffer
 
 	rf, formatter, err := grpcurl.RequestParserAndFormatterFor(grpcurl.Format("json"), r.descSource, false, true, in)
 	if err != nil {
 		return "", 0, err
 	}
-	h := grpcurl.NewDefaultEventHandler(os.Stdout, r.descSource, formatter, false)
+	h := grpcurl.NewDefaultEventHandler(&resultBuffer, r.descSource, formatter, false)
 
 	start := time.Now()
 	err = grpcurl.InvokeRPC(ctx, r.descSource, r.clientConn, symbol, r.headers, h, rf.Next)
 	end := time.Now().Sub(start) / time.Millisecond
-	w.Close()
 	if err != nil {
 		return "", end, err
 	}
@@ -231,9 +210,7 @@ func (r *Resource) Invoke(ctx context.Context, symbol string, in io.Reader) (str
 		return "", end, fmt.Errorf(h.Status.Message())
 	}
 
-	out := <-outC
-
-	return out, end, nil
+	return resultBuffer.String(), end, nil
 }
 
 // Close - to close all resources that was opened before