Skip to content

Instantly share code, notes, and snippets.

Roger Peppe rogpeppe

Block or report user

Report or block rogpeppe

Hide content and notifications from this user.

Learn more about blocking users

Contact Support about this user’s behavior.

Learn more about reporting abuse

Report abuse
View GitHub Profile
View workshop-chat.proto
syntax = "proto3";
package main;
option go_package = "main";
service Chat {
// NewUser creates a new user account.
// It returns a token that acts as a password for
// the user and the IP address of the user client.

Go Modules Workshop

The aim of this workshop is to familiarise you with the basics of Go modules. By the end, you should know how to:

  • build a project that uses modules
  • create a project that uses modules
  • keep module dependencies up to date
  • manage module dependencies, exclusions and replacements
  • deal with dependencies that don't use Go modules

Some thoughts about the draft Go error inspection design

Some error packages intend for programs to act on a single error (the “Cause”) extracted from the chain of wrapped errors. We feel that a single error is too limited a view into the error chain.

It might not feel that way initially, but I believe that a single error is almost as expressive as iterating down the stack looking for an error that fits some criteria, and considerably easier to reason about.

rogpeppe /
Last active Jun 7, 2019
go get binary@version
# This command installs binaries at specified versions
# into $GOBIN, $GOPATH/bin or $HOME/bin.
# It assumes Go 1.11.
if [ $# = 0 ]; then
usage: vgoget cmdpackage[@version]... >&2
exit 2
d=`mktemp -d`
cd "$d"
rogpeppe /
Last active Sep 14, 2018
Go Contracts as type structs

Go contracts as type structs

Roger Peppe, 2018-09-05

In my previous post, I talked about an issue with a real world use case for contracts - the fact that all type parameters must be mentioned every time a contract is used in a definition. In this post, I introduce an idea for a possible way to fix this.

The most important feature of contracts, in my view,

rogpeppe /
Last active Mar 2, 2019
Go contracts use case: generic mgo

Go contracts use case: generic mgo

Roger Peppe, 2018-09-05

Most of the discussion about the new Go contracts proposal has been centred around hypothetical or small-scale examples. As Go is a language that's designed for programming in the large, I thought it might be interesting to see how contracts fitted with a more real-world example.


rogpeppe /
Last active Apr 9, 2019
Go generics at runtime (part 2 of 2)

Go generics at runtime (part 2 of 2)

In my previous post, I talked about some of the underlying runtime concepts behind generics in Go.

Here I'll go a bit deeper into how we might, in principle, be able to compile a generic function once for many instantiated types.

What functions do we need to compile?


Go generics at runtime (part 1 of 2)

From the design document:

Generic functions, rather than generic types, can probably be compiled using an interface-based approach. That will optimize compile time, in that the package is only compiled once, but there will be some run-time cost.

Generic types may most naturally be compiled multiple times for each


Operator overloading in Go with contracts

Roger Peppe 2018-09-03

[Edit 2018-09-11 Reworked following feedback from @jba]

In his Go generics feedback document, Dominic Honnef writes "Contracts are nice, but where is the operator overloading?". In this document, I set down some thoughts about how operator overloading might be added to Go within the context of the new generics design, layered on top of the current design.

The central part would be a new package in the standard library. This package would hook a type-parameterized type up to chosen Go operators. The Go compiler would know how to rewrite operator syntax into method call syntax on associated interface methods. How that's done is implementation-defined, and the API itself is defined by a package, but contracts supply a way of reasoning about available operators without defining the mapping between operators and method names.

The compiler would be responsible for making sure exist


Revised generics design

Roger Peppe, 2018-09-01

One common response to the new generics design has been that contracts seem a bit too much like interfaces but not the same.

They are indeed very similar if you squint a little. Consider these two definitions:

type IReader interface {
	Read([]byte)(int, error)
You can’t perform that action at this time.