Error Handling

Defer, Panic, and Recover in Go Explained Defer schedules cleanup, panic halts execution for errors, and recover catches panics to restore normal flow. Error handling best practices Handle errors in Go by explicitly checking return values and using the error interface to manage failures gracefully. Errors in goroutines Fix goroutine errors in Go by using the race detector and ensuring proper synchronization and exit paths. errors.Is vs errors.As Use errors.Is to check for specific error values and errors.As to extract custom error types from wrapped chains. Fix: "context canceled" Fix context canceled errors by checking ctx.Err() and handling the cancellation signal gracefully in your Go code. Fix: "context deadline exceeded" Fix context deadline exceeded by increasing the timeout duration in context.WithTimeout or optimizing the slow operation. Fix: "error is not nil but has a nil value" (Nil Interface Gotcha) Fix the Go nil interface error by checking if the underlying value is nil before calling methods on the error. Fix: "sql: no rows in result set" Fix sql: no rows in result set by checking for sql.ErrNoRows after Scan() or using Query() for multiple results. fmt Errorf with %w Use the %w verb in fmt.Errorf to wrap errors, preserving the error chain for errors.Is and errors.As checks. Go Error Handling Patterns and Best Practices Go uses explicit error returns requiring immediate checks with if err != nil to handle failures without exceptions. Go Idioms: Errors Are Values Go treats errors as return values that you check explicitly, allowing precise control over failure handling without exceptions. How does error handling work in Go Go handles errors by returning them as a second value that callers must explicitly check before proceeding. How Error Handling Works in Go (No Exceptions) Go handles errors by returning them as explicit values that developers must check, avoiding the complexity and hidden control flow of exceptions. How to Add Context to Errors in Go Use fmt.Errorf with the %w verb to wrap Go errors with context while maintaining the error chain for unwrapping. How to Create an Error Chain in Go Create an error chain in Go by wrapping errors with fmt.Errorf and the %w verb to preserve the original error context. How to Create a Sentinel Error in Go Create a sentinel error by declaring a package-level variable of type `error` and assigning it a value created with `errors.New()`. How to create custom error types Create a custom error type in Go by defining a struct with an Error() method and returning it from your functions. How to Create Custom Error Types in Go Create a custom error type in Go by defining a struct with an Error() method to return a descriptive string. How to Create Error Types with Stack Traces in Go Create a custom error type in Go that captures the call stack using runtime.Callers to include stack traces in error messages. How to Handle Errors Idiomatically in Go Handle errors in Go by checking return values immediately, using errors.Is for specific types, and wrapping errors with fmt.Errorf to preserve context. How to Handle Errors in Deferred Functions Defer statements cannot prevent error returns; handle errors immediately after the call or use defer only for cleanup and logging. How to Handle Errors in Goroutines Handle goroutine errors by sending results via channels or using defer with recover to catch panics. How to Handle Errors in gRPC with Go Handle gRPC errors in Go by checking the error return value and using status.FromError to extract the code and message. How to Handle Multiple Errors in Go Combine multiple Go errors into a single return value using errors.Join to report all failures without stopping execution. How to Implement Graceful Degradation in Go Services Implement graceful degradation in Go by wrapping risky calls in defer/recover blocks to catch panics and return safe fallback data. How to Implement the error Interface for Custom Errors Implement the error interface in Go by adding an Error() method that returns a string to your custom type. How to Implement the error Interface in Go Implement the error interface in Go by defining a type with an Error() string method. How to Log and Handle Errors Properly in Go Log errors with context using log.Printf and handle them by returning or exiting to prevent silent failures. How to Return and Check Errors in Go In Go, functions return errors as a second (or final) return value, and you must explicitly check them using `if err != nil` before proceeding. How to Return an Error from a Function in Go Return errors in Go by adding 'error' to the function signature and returning an error value created with errors.New or fmt.Errorf. How to Structure Error Messages in Go (lowercase, no punctuation) Use lowercase error messages without terminal punctuation to align with Go standard library conventions. How to Unwrap Errors in Go with errors.Unwrap Use errors.Unwrap to access the underlying error in a chain, or errors.Is and errors.As to check for specific error types. How to Use errgroup for Concurrent Error Handling Use errgroup.WithContext to run goroutines concurrently and automatically cancel them on the first error. How to Use errors.As in Go Use errors.As to check if an error matches a specific type and extract its concrete value for detailed handling. How to Use errors.Is in Go Use errors.Is to check if an error matches a specific target or wraps it in Go. How to Use errors.New and fmt.Errorf in Go Use errors.New for static messages and fmt.Errorf for formatted or wrapped errors with context. How to Use panic and recover in Go Use panic to stop execution on critical errors and recover in a deferred function to catch and handle them gracefully. How to Use the defer Keyword in Go The defer keyword in Go schedules a function call to run immediately before the surrounding function returns, ensuring reliable resource cleanup. How to Use the errors.Join Function in Go 1.20+ errors.Join combines multiple Go errors into a single error value for unified handling and inspection. How to wrap errors Use `fmt.Errorf` with the `%w` verb to wrap errors, which preserves the original error's type and message while adding context. How to Wrap Errors in Go with %w Use fmt.Errorf with the %w verb to wrap Go errors and preserve the original error chain for debugging. if err != nil: Common Patterns and Shortcuts Handle Go errors by checking `if err != nil` and returning or logging immediately to prevent further execution with invalid data. Implementing error interface Implement the error interface by defining a type with an Error() string method to return a custom error message. multierr package Use errors.Join from the standard library to combine multiple errors into a single error value for better debugging. Sentinel error pattern The sentinel error pattern defines a unique error variable to identify specific failure conditions for precise error handling. What Is the Difference Between errors.Is and errors.As errors.Is checks for a specific error value, while errors.As extracts a custom error type to access its fields. When to use panic Use panic only for unrecoverable errors where the program cannot safely continue execution. When to Use panic vs Returning an Error in Go Return errors for recoverable issues and panic only for unrecoverable logic failures or fatal system errors. Why Go Doesn't Have try/catch and What to Use Instead Go omits try/catch to enforce explicit error checking via return values and if statements.