Example of github.com/pkg/errors

example.go

package main

import (
	"fmt"

	"github.com/pkg/errors"
)

func A() error {
	// New errors created with pkg/errors.New() will include a full
	// stack trace.
	return errors.New("blam")
}

func B() error {
	// No need to wrap/trace at every return, just a point of error
	// creation.
	return A()
}

func C() error {
	// Pre-existing errors may be wrapped to add more detail.
	return errors.Wrap(B(), "foo")
}

func D() error {
	return C()
}

func main() {
	err := D()
	fmt.Printf("# Value:\n %v\n\n", err)
	
	// Formatting with %+v produces stack trace.
	fmt.Printf("# Extended value:\n%+v\n\n", err) 
	
	// errors.Cause() provides access to original error.
	fmt.Printf("# Cause: %v\n", errors.Cause(err))
	fmt.Printf("# Extended Cause:\n%+v\n", errors.Cause(err))
}

/* Example output:

# Value:
 foo: blam

# Extended value:
blam
main.A
	/home/menno/go/src/sandbox/errs/main.go:12
main.B
	/home/menno/go/src/sandbox/errs/main.go:18
main.C
	/home/menno/go/src/sandbox/errs/main.go:23
main.D
	/home/menno/go/src/sandbox/errs/main.go:27
main.main
	/home/menno/go/src/sandbox/errs/main.go:31
runtime.main
	/snap/go/327/src/runtime/proc.go:185
runtime.goexit
	/snap/go/327/src/runtime/asm_amd64.s:2197
foo
main.C
	/home/menno/go/src/sandbox/errs/main.go:23
main.D
	/home/menno/go/src/sandbox/errs/main.go:27
main.main
	/home/menno/go/src/sandbox/errs/main.go:31
runtime.main
	/snap/go/327/src/runtime/proc.go:185
runtime.goexit
	/snap/go/327/src/runtime/asm_amd64.s:2197

# Cause: blam
# Extended Cause:
blam
main.A
	/home/menno/go/src/sandbox/errs/main.go:12
main.B
	/home/menno/go/src/sandbox/errs/main.go:18
main.C
	/home/menno/go/src/sandbox/errs/main.go:23
main.D
	/home/menno/go/src/sandbox/errs/main.go:27
main.main
	/home/menno/go/src/sandbox/errs/main.go:31
runtime.main
	/snap/go/327/src/runtime/proc.go:185
runtime.goexit
	/snap/go/327/src/runtime/asm_amd64.s:2197

*/