build error utility package to replace juju/errors

Signed-off-by: Bruce Ma <brucema19901024@gmail.com>

pkg/errors/errors.go

@@ -0,0 +1,38 @@
+// Copyright 2020 CNI authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package errors
+
+import "fmt"
+
+
+// Annotate is used to add extra context to an existing error. The return will be
+// a new error which carries error message from both context message and existing error.
+func Annotate(err error, message string) error {
+	if err == nil {
+		return nil
+	}
+
+	return fmt.Errorf("%s: %v", message, err)
+}
+
+// Annotatef is used to add extra context with args to an existing error. The return will be
+// a new error which carries error message from both context message and existing error.
+func Annotatef(err error, message string, args ...interface{}) error {
+	if err == nil {
+		return nil
+	}
+
+	return fmt.Errorf("%s: %v", fmt.Sprintf(message, args...), err)
+}