[throwawayfuzz]

If you want this behavior, you can just panic if an error is returned. Or you can divide the set of errors into expected and unexpected kinds, and panic only on the unexpected ones.

But the main reason this is the case is because in Go, errors are things that can arise from correctly behaving functions. If someone passes you invalid input, it's correct to return an error. You wouldn't want this to show up in as bad input in a fuzzer. Most fuzz test cases after all will not be correct input.