feat: Add a public method to determine if the error has been appended to the stack.

[wbflooksky]

feat func ExistStack(err error) bool:

non-intrusive:
Add a public method to determine if the error has been appended to the stack.
Avoid adding the stack repeatedly for errors.

fix: error method

feat: test ExistStack

add ExistStack test

fix: error variable name

style: optimizing code structure

feat: add test example

style(value): delete func reachable code

style(build): edit format files

[wbflooksky]

fix: #210

[puellanivis]

The previous PR was already closed as “will not merge” #239 and this has no changes that we could not have come to through a code review process. (My code review was intended to help you write better code, not to get it to a state that would be merged. Sorry if it gave you a false impression.)

Please read the project’s README:

Because of the Go2 errors changes, this package is not accepting proposals for new functionality.

[wbflooksky]

ok