As finds the first error in err's tree that matches target, and if one is found, sets target to that error value and returns true.

Caller returns a Frame that describes a frame on the caller's stack.

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

FormatError calls the FormatError method of f with an errors.Printer configured according to s and verb, and writes the result to s.

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

New returns an error that formats as the given text.

Opaque returns an error with the same error formatting as err but that does not match err and cannot be unwrapped.

Unwrap returns the result of calling the Unwrap method on err, if err implements Unwrap.

A Frame contains part of a call stack.

A Formatter formats error messages.

A Printer formats error messages.

A Wrapper provides context around another error.