Add errors package for exit code handling

To get a better exit code handling including logrus logging I have
defined a custom errors package which uses logrus to log error messages.

errors/errors.go

@@ -0,0 +1,73 @@
+package errors
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/sirupsen/logrus"
+)
+
+// ExitCoder defines the interface for exit code handling.
+type ExitCoder interface {
+	error
+	Code() int
+	Fields() logrus.Fields
+}
+
+// ExitError simply implements the defined interface.
+type ExitError struct {
+	message interface{}
+	code    int
+	fields  logrus.Fields
+}
+
+// Error implements the ExitCoder interface.
+func (e ExitError) Error() string {
+	return fmt.Sprintf("%v", e.message)
+}
+
+// Code implements the ExitCoder interface.
+func (e ExitError) Code() int {
+	return e.code
+}
+
+// Fields implements the ExitCoder interface.
+func (e ExitError) Fields() logrus.Fields {
+	return e.fields
+}
+
+// ExitMessage initiales a new ExitCoder implementation.
+func ExitMessage(message interface{}) ExitError {
+	return ExitError{
+		message: message,
+		code:    1,
+	}
+}
+
+// WithFields initiales a new ExitCoder implementation.
+func WithFields(message interface{}, fields logrus.Fields) ExitError {
+	return ExitError{
+		message: message,
+		code:    1,
+		fields:  fields,
+	}
+}
+
+// HandleExit ist used within the main handler to exit properly.
+func HandleExit(err error) {
+	if err == nil {
+		return
+	}
+
+	if e, ok := err.(ExitCoder); ok {
+		if e.Error() != "" {
+			logrus.WithFields(
+				e.Fields(),
+			).Error(
+				e.Error(),
+			)
+		}
+
+		os.Exit(e.Code())
+	}
+}