errlog: Index | Files

package errlog

import ""

Package errlog provides a simple object to enhance Go source code debugging

Example result:

$ go run myfailingapp.go
Program starting
error in main.main: something failed here
line 13 of /Users/snwfdhmp/go/src/
9: func main() {
10:     fmt.Println("Program starting")
11:     err := errors.New("something failed here")
13:     errlog.Debug(err)
15:     fmt.Println("End of the program")
16: }
exit status 1

You can configure your own logger with these options :

type Config struct {
	LinesBefore        int
	LinesAfter         int
	PrintStack         bool
	PrintSource        bool
	PrintError         bool
	ExitOnDebugSuccess bool

Example :

debug := errlog.NewLogger(&errlog.Config{
	LinesBefore:        2,
	LinesAfter:         1,
	PrintError:         true,
	PrintSource:        true,
	PrintStack:         false,
	ExitOnDebugSuccess: true,

// ...
if err != nil {

Outputs :

Error in main.someBigFunction(): I'm failing for no reason
line 41 of /Users/snwfdhmp/go/src/
33: func someBigFunction() {
40:     if err := someNastyFunction(); err != nil {
41:             debug.Debug(err)
42:             return
43:     }
exit status 1


Package Files

defaults.go errlog.go logger.go regexp.go utils.go


const (
    // ModeDisabled represents the disabled mode (NO-OP)
    ModeDisabled = iota + 1
    // ModeEnabled represents the enabled mode (Print)


var (
    //DefaultLoggerPrintFunc is fmt.Printf without return values
    DefaultLoggerPrintFunc = func(format string, data ...interface{}) {
        fmt.Printf(format+"\n", data...)

    //DefaultLogger logger implements default configuration for a logger
    DefaultLogger = &logger{
        config: &Config{
            PrintFunc:          DefaultLoggerPrintFunc,
            LinesBefore:        4,
            LinesAfter:         2,
            PrintStack:         false,
            PrintSource:        true,
            PrintError:         true,
            ExitOnDebugSuccess: false,

func Debug Uses

func Debug(uErr error) bool

Debug is a shortcut for DefaultLogger.Debug.

func PrintRawStack Uses

func PrintRawStack()

PrintRawStack prints the current stack trace unparsed

func PrintStack Uses

func PrintStack()

PrintStack pretty prints the current stack trace

func PrintStackMinus Uses

func PrintStackMinus(depthToRemove int)

PrintStackMinus prints the current stack trace minus the amount of depth in parameter

func SetDebugMode Uses

func SetDebugMode(toggle bool)

SetDebugMode sets debug mode to On if toggle==true or Off if toggle==false. It changes log level an so displays more logs about whats happening. Useful for debugging.

type Config Uses

type Config struct {
    PrintFunc               func(format string, data ...interface{}) //Printer func (eg: fmt.Printf)
    LinesBefore             int                                      //How many lines to print *before* the error line when printing source code
    LinesAfter              int                                      //How many lines to print *after* the error line when printing source code
    PrintStack              bool                                     //Shall we print stack trace ? yes/no
    PrintSource             bool                                     //Shall we print source code along ? yes/no
    PrintError              bool                                     //Shall we print the error of Debug(err) ? yes/no
    ExitOnDebugSuccess      bool                                     //Shall we os.Exit(1) after Debug has finished logging everything ? (doesn't happen when err is nil)
    DisableStackIndentation bool                                     //Shall we print stack vertically instead of indented
    Mode                    int

Config holds the configuration for a logger

type Logger Uses

type Logger interface {
    // Debug wraps up Logger debugging funcs related to an error
    // If the given error is nil, it returns immediately
    // It relies on Logger.Config to determine what will be printed or executed
    // It returns whether err != nil
    Debug(err error) bool
    //PrintSource prints lines based on given opts (see PrintSourceOptions type definition)
    PrintSource(lines []string, opts PrintSourceOptions)
    //DebugSource debugs a source file
    DebugSource(filename string, lineNumber int)
    //SetConfig replaces current config with the given one
    SetConfig(cfg *Config)
    //Config returns current config
    Config() *Config
    //Disable is used to disable Logger (every call to this Logger will perform NO-OP (no operation)) and return instantly
    //Use Disable(true) to disable and Disable(false) to enable again

Logger interface allows to log an error, or to print source code lines. Check out NewLogger function to learn more about Logger objects and Config.

func NewLogger Uses

func NewLogger(cfg *Config) Logger

NewLogger creates a new logger struct with given config

type PrintSourceOptions Uses

type PrintSourceOptions struct {
    FuncLine    int
    StartLine   int
    EndLine     int
    Highlighted map[int][]int //map[lineIndex][columnstart, columnEnd] of chars to highlight

PrintSourceOptions represents config for (*logger).PrintSource func

type StackTraceItem Uses

type StackTraceItem struct {
    CallingObject string
    Args          []string
    SourcePathRef string
    SourceLineRef int
    MysteryNumber int64

StackTraceItem represents parsed information of a stack trace item

Package errlog imports 9 packages (graph) and is imported by 3 packages. Updated 2019-08-09. Refresh now. Tools for package owners.