How do you handle errors returned from functions that implement the `error` interface?

You use the `if err != nil` statement to check for errors. If an error is present, you can handle it using a `return` statement to return the error, or by logging it and continuing execution. For example: `if err != nil { return err }` or `log.Println(err)`. Consider using `defer` to ensure error handling is performed even if the function returns early.