How to Properly Handle Errors Returned by Defer in Go?

Error Handling and Deferrals

In Go, the defer statement is commonly used to execute a function or cleanup operation after the surrounding function returns. However, if the deferred function returns an error, it may be overlooked due to the typical practice of ignoring the error returned by defer, which can lead to unexpected system behavior.

Consider the following scenario:

OpenDbConnection(connectionString string, logSql bool) (*gorm.DB, error) {
    logger := zap.NewExample().Sugar()
    defer logger.Sync()
}

In this example, the logger.Sync() method may return an error that is ignored, leaving potential issues unresolved.

Possible Strategies

• Use a named error variable: Initialize an error variable within the function scope and assign the error returned by the deferred function to it. This allows the error to be inspected and handled as needed.
• Callable argument-less deferred function: Enclose the deferred function within an anonymous function without arguments. This allows the deferred function to return an error, which can then be assigned to the named error variable.
• Return the error and handle it in the calling function: Return the error from the function and let the calling function handle it appropriately. This may be preferred if the error requires special handling or analysis.

Here is an example using the named error variable strategy:

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

    // ... rest of function logic ...

    return db, err
}

With this approach, the error can be checked and handled in the calling function:

db, err := OpenDbConnection(connectionString, logSql)
if err != nil {
    // Handle the error
}

The above is the detailed content of How to Properly Handle Errors Returned by Defer in Go?. For more information, please follow other related articles on the PHP Chinese website!