Package errors builds on Go 1.13 errors adding HTTP and GRPC code to your errors. Wrap() and Wrapf() When the wrap functions are used with one of the defined Err* constants you get back an error that you're able to pass the error through a GRPC server and client or use to build HTTP error messages and set the HTTP status. Wrapping any error other than an Error will return an error with the message formatted as "<message>: <error>". Wrapping an Error will return an error with an unaltered error message. The errors produced with wrap, that have also been wrapped first with an Err* can be send with SendGRPCError() and received with ReceiveGRPCError(). You may want to create and use GRPC server and client interceptors to avoid having to call the Send/Receive methods in every handler. The Err* constants are errors and can be used directly is desired.