Cause returns the underlying cause of the error, if possible.

Errorf formats according to a format specifier and returns the string as a value that satisfies error.

New returns an error with the supplied message.

WithStack annotates err with a stack trace at the point WithStack was called.

Wrap annotates err with a new message.

Wrapf annotates err with the format specifier.

ErrorList is a wrapper over list of errors It implements error interface.