The built-in recover function is only useful inside deferred functions. Calling it in a function that is never deferred means that it will always return nil and it will never regain control of a panicking goroutine. The same is true of calling recover directly in a defer statement.

Carefully inspect the code to determine whether it is a mistake that should be fixed.

In the example below, the function fun1 is intended to recover from the panic. However, the function that is deferred calls another function, which then calls recover:

This problem can be fixed by deferring the call to the function which calls recover:

In the following example, recover is called directly in a defer statement, which has no effect, so the panic is not caught.

We can fix this by instead deferring an anonymous function which calls recover.

Defer, Panic, and Recover - The Go Blog.