The Go Programming Language

5.4 Errors

Some functions always succeed at their task. For example, strings.Contains and strconv.FormatBool have well-defined results for all possible argument values and cannot fail—barring catastrophic and unpredictable scenarios like running out of memory, where the symptom is far from the cause and from which there’s little hope of recovery.

Other functions always succeed so long as their preconditions are met. For example, the time.Date function always constructs a time.Time from its components—year, month, and so on—unless the last argument (the time zone) is nil, in which case it panics. This panic is a sure sign of a bug in the calling code and should never happen in a well-written program.

For many other functions, even in a well-written ...