How Can You Effectively Handle Errors Returned from Defer Statements in Go?

Error Handling in Defer with Deferred Error Variables

In Go, defer statements are used to ensure the execution of a function after the surrounding function has returned. This is useful for cleanup tasks or resource management. However, what happens when a defer statement returns an error?

Handling Deferred Errors

Consider a function that attempts to open a database connection and returns either the connection or an error. The function uses a logger that must be synced before exiting. The logger's Sync() method returns an error that is currently being ignored.

Best Practices

The recommended approach to handling deferred errors is to name and initialize the returning error variable anywhere inside the function. By naming the error variable, it becomes easier to track errors during testing and debugging.

For instance, the original code can be modified as follows:

func OpenDbConnection(connectionString string, logSql bool) (*gorm.DB, error) {
    logger := zap.NewExample().Sugar()
    defer func() {
        if err := logger.Sync(); err != nil {
            return
        }
    }()

    // some logic here

    return db, err
}

Advantages

This approach has several advantages:

• Errors are correctly returned to the caller.
• Errors are tracked during testing and debugging.
• The code is easier to read and understand.

Conclusion

When handling deferred errors, it is best practice to name and initialize the returning error variable inside the function. This allows for proper error handling and simplifies debugging.

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