error

Overview ¶

errors demonstrates error handling in Go

• Some functions always succeeds so they don't need to return errors.
• Some functions always returns single failure, so a bool can be used.
• An "error" type of argument is required if a function can return multiple errors.
• The other return values are undefined when an error is returned. However, some functions may need to return partial results along with the error. Say a Read() returning partial data with IO errors. Such case should be documented well.

Go took the design decision to go with this error type instead of exceptions:

• Exceptions returns incomprehensible stacktrace, full of information about the structure of the program, but lacking intelligable context about what went wrong.
• By contrast, Go programs use ordinary error handling with return values and if statements. The demands more attention to be paid to error handling. This is the primary reason.
• Go also has panic() and recover() which is a kind of exception handling, but that is used to report truly unexpected exceptions that indicates a bug.

The error type is an interface:

• A nil value is default and indicates no error.
• it has the method "Error() string" to get the error message.
• Package "errors" contains several helpers
• fmt.Errorf is handy to produce error type that uses Sprintf internally

Error handling techniques:

1. Propagate the error a. Return as it is b. Add context to the error and form the chain
2. Retry for sometime
3. Exit with error code (main workflow)
4. Ignore the error continue with limited functionality
5. Ignore the error and proceed

In general, get into the habit of handling errors returned by functions.

• If you deliberately ignore some errors, document it.
• Handle the error first before performing success action
• If return statement is used for error, then write the success action in the outer block. Do not use else block and minimize in indent.
• So a function tends to handle multiple errors on top and return. Finally the sustance of the function.