github.com/friendsofgo/errors (go): Original package created by Dave Cheney Copyright (c) 2015, Dave Cheney <dave@cheney.net>  Modifications of the original package by Friends of Go Copyright (c) 2019, Friends of Go <contact@friendsofgo.tech>  Package errors provides simple error handling primitives.  The traditional error handling idiom in Go is roughly akin to  which when applied recursively up the call stack results in error reports without context or debugging information. The errors package allows programmers to add context to the failure path in their code in a way that does not destroy the original value of the error.  The errors.Wrap function returns a new error that adds context to the original error by recording a stack trace at the point Wrap is called, together with the supplied message. For example  If additional control is required, the errors.WithStack and errors.WithMessage functions destructure errors.Wrap into its component operations: annotating an error with a stack trace and with a message, respectively.  Using errors.Wrap constructs a stack of errors, adding context to the preceding error. Depending on the nature of the error it may be necessary to reverse the operation of errors.Wrap to retrieve the original error for inspection. Any error value which implements this interface  can be inspected by errors.Cause. errors.Cause will recursively retrieve the topmost error that does not implement causer, which is assumed to be the original cause. For example:  Although the causer interface is not exported by this package, it is considered a part of its stable public interface.  With the new standard package error we have two new ways to figure what is the cause of our error:  or even with sentinel errors:  All error values returned from this package implement fmt.Formatter and can be formatted by the fmt package. The following verbs are supported:  New, Errorf, Wrap, and Wrapf record a stack trace at the point they are invoked. This information can be retrieved with the following interface:  The returned errors.StackTrace type is defined as  The Frame type represents a call site in the stack trace. Frame supports the fmt.Formatter interface that can be used for printing information about the stack trace of this error. For example:  Although the stackTracer interface is not exported by this package, it is considered a part of its stable public interface.  See the documentation for Frame.Format for more details.
Keywords: go|go-errors|golang|golang-errors