When is it Appropriate to Use `log.Fatal` in Go?

When to Use log.Fatal in Go

log.Fatal terminates the application with a non-zero exit code after printing an error message. While it's generally discouraged to use log.Fatal in non-main functions, there are specific scenarios where its use is appropriate.

Best Practices

According to the standard library documentation, log.Fatal should primarily be used in main or init functions to ensure immediate termination in case of critical errors before the application's main functionality is executed.

Exceptions

However, there are exceptions to this rule:

• Irrecoverable Errors: If an error occurs that cannot be reasonably recovered from, using log.Fatal is appropriate. An example could be an error while initializing a critical dependency that renders the application unusable.
• Unrecoverable Processes: Use log.Fatal when you encounter an error during a process that cannot be safely reversed. For instance, if a directory copy operation encounters a file conflict that cannot be resolved without user intervention, log.Fatal can be used to explain the situation and terminate the process.

Example:

The net/http package uses log.Fatal to terminate the application if a duplicate idle connection is detected in the freelist, which is a critical error that should be reported and corrected immediately.

Conclusion

While log.Fatal should generally be avoided in non-main functions, it remains a valuable tool for reporting and terminating the application in the face of critical and irrecoverable errors. By following the best practices outlined above, developers can ensure the proper usage of log.Fatal in Go applications.

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