package mainimport ("fmt"//    "testing"
)var Pkg = "packageName"type Err struct {Pkg  stringInfo stringPrev error
}func (e *Err) Error() string {if e.Prev == nil {return fmt.Sprintf("%s: %s", e.Pkg, e.Info)}return fmt.Sprintf("%s: %s\n%v", e.Pkg, e.Info, e.Prev)
}func me(err error, format string, args ...interface{}) *Err {if len(args) > 0 {return &Err{Pkg:  Pkg,Info: fmt.Sprintf(format, args...),Prev: err,}}return &Err{Pkg:  Pkg,Info: format,Prev: err,}
}func ce(err error, format string, args ...interface{}) {if err != nil {panic(me(err, format, args...))}
}func ct(err *error) {if p := recover(); p != nil {if e, ok := p.(error); ok {*err = e} else {panic(p)}}
}func oe(e error) error {var ret error = efor err, ok := ret.(*Err); ok && err.Prev != nil; err, ok = ret.(*Err) {ret = err.Prev}return ret
}func foo() (err error) {defer ct(&err)ce(bar(), "call bar")return
}func bar() (err error) {defer ct(&err)ce(baz(), "call baz")return
}func baz() (err error) {return me(nil, "baz")
}func main() {ce(foo(), "call foo")
}

panic: packageName: call foo
packageName: call bar
packageName: call baz
packageName: bazgoroutine 1 [running]:
panic(0x491000, 0xc420016300)/opt/golang/go/src/runtime/panic.go:500 +0x1a1
main.ce(0x4f9140, 0xc4200162d0, 0x4a741f, 0x8, 0x0, 0x0, 0x0)/opt/golang/workspace/src/github.com/junneyang/letsgo/error_test/error_common.go:40 +0x97
main.main()/opt/golang/workspace/src/github.com/junneyang/letsgo/error_test/error_common.go:79 +0x69
Error: process exited with code 2.