As finds the first error in err's chain that matches target, and if so, sets target to that error value and returns true.

Is reports whether any error in err's chain matches target.

NewSentinel acts as New but does not add stack frame.

NextStackTracer returns next error with stack trace.

StackTraceOfCause returns first stacktrace that was added to error chain (closest to the root error).

StackTraceOfEffect returns last stacktrace that was added to error chain (furthest from the root error).

Unwrap returns the result of calling the Unwrap method on err, if err's type contains an Unwrap method returning error.

Sentinel error.

Wrapper provides context around another error.