golang: How to Add Better Context to Errors

There are at least three ways to add more context to errors.

1. fmt.Errorf
2. errors package
3. zap library

package main

import (
	"errors"
	"fmt"

	werr "github.com/pkg/errors"
	"go.uber.org/zap"
)

// 1. wraps with a message
func wrap(e error) error {
	return fmt.Errorf("another layer - %w", e)
}

// 2. wraps with callstack and message
func betterWrap(e error) error {
	return werr.Wrap(e, "a better layer")
}

// 3. wraps with the first callstack frame
func zapLogger(e error) {
	logger, _ := zap.NewProduction()
	defer logger.Sync()
	logger.Info("failed to fetch URL",
		// Structured context as strongly typed Field values.
		zap.Error(e))
}

func main() {
	e := errors.New("a test err")

	fmt.Printf("err= %+v\n", wrap(e))
	fmt.Printf("%+v\n", betterWrap(e))
	zapLogger(e)
}

Execution

 $ go run err_context.go

fmt.errorf

err= another layer - a test err

errors package

a test err
a better layer
main.betterWrap
        /Users/xxx/go-code/blog/err/err_context.go:18
main.main
        /Users/xxx/go-code/blog/err/err_context.go:35
runtime.main
        /Users/xxx/.goenv/versions/1.14.0/src/runtime/proc.go:203
runtime.goexit
        /Users/xxx/.goenv/versions/1.14.0/src/runtime/asm_amd64.s:1373

zap

{"level":"info","ts":1604374256.270431,"caller":"err/err_context.go:25",
"msg":"failed to fetch URL","error":"a test err"}

Conclusion

I like the errors package the most. It has a relevant context to troubleshoot a problem.