在Golang中导入模块时如何捕获错误？

Question

In golang, when I import a module, its init() gets executed (before main() I assume?), it is possible some error is generated in this function. How can I capture these errors and handle them in my own code?

Answer 1

Yes, package init() functions run before the main() function, see Package initialization in the language specification.

And no, you can't handle errors occurred in package init() functions. Even if you could, that would mean a package your program depends on failed to initialize and you wouldn't know what to expect from it.

Package init() functions have no return values and they can't panic in a meaningful way that was meant to recover from. If an init() function panics, the program terminates.

Since init() functions are not called by you (e.g. from the main() function), you can't recover from there. It is the responsibility of the package itself to handle errors during its initialization, not the users of the package.

One option to signal error happening during an init() is to store the error state in a variable (e.g. exported, or unexported but queryable by an exported function). But this should be used only if it is reasonable to continue, and this is also the task/responsibility of the package itself (to store/report the error) and not the users of the package. You can't do this without the cooperation of the package (you can't "catch" unhandled/unreported errors and panics).