How to get the stack trace pointing to actual error reason

Question

Let's say I have some code like this:

value, err := some3rdpartylib.DoSomething() if err != nil {     panic(err) } 

In case err != nil I will get something like this:

panic: some error explanation here  goroutine 1 [running]: main.main()     /tmp/blabla/main.go:6 +0x80 

This stack trace is completely legit but sometimes these error messages may not clarify what happened and so I'd like to dig deeper into the source code of the 3rd party library to investigate what exactly causes this error to be returned. However when my code panics like this, there is no way to get the actual place that returned this error.

A little bit more clarification: as I'm coming from JVM world where exceptions are thrown I can completely trace what exactly line of code thrown the exception and thus can easily find the place and see what gone wrong. Go stack trace ends exactly where my code panics and thus not too useful in my case.

I've created a playground here and ideally I'd like to be able to trace the error to the place it was actually returned from, not panic. (e.g. to line 17, return "", errors.New("some error explanation here"))

Is this even possible?

Answer 1

I think that there is an easier way to achieve this. You can try wrapping errors using the golang "default" third party library error package:

You need to define the interface to be implemented by your error :

type stackTracer interface {     StackTrace() errors.StackTrace } 

Then use it when wrapping/processing an error :

err, ok := errors.(stackTracer) // ok is false if errors doesn't implement stackTracer  stack := err.StackTrace() fmt.Println(stack) // here you'll have your stack trace 

Answer 2

Shortly: this is not possible. Since errors are values, they are not treated in any special way. Due to this, when function (normally) returns, stack is no more available (ie. another function call may overwrite memory used by returning-error function' stack).

There is a tool called trace which was introduced with go1.5, but for now, there is no comprehensive tutorial available neither any of those I found says that this kind of feature will be included.