Golang to C# Converter

Converts source code developed using the Go programming language (see Go Language Specification) to the C# programming language (see C# Language Specification).

News

• Project has been updated to use .NET 7.0 / C# 11

• String literals are encoded using UTF-8 (C# u8 string suffix) which uses ReadOnlySpan<byte> ref struct. This should make Go strings faster since strings do not have to be converted to UTF8 from UTF16. Also added an experimental sstring which is a ref struct implementation of a Go string.

• Code conversions now better match original Go code styling

• Recent example usages of go2cs allow the use of Golang as the scripting language for the Unity and Godot game engine platforms. See the GoUnity and GodotGo projects.

Goals

• Convert Go code into C# so that Go code can be directly used within .NET ecosystem.
  • This is the primary goal of go2cs.
• Convert Go code into behaviorally and visually similar C# code – see conversion strategies.
  • Code conversions focus first on making sure C# code runs as behaviorally similar to Go code as possible. This means, for now, leaving out things like code conversions into async functions. Instead conversions make things operate the way they do in Go, e.g., simply running a function on the current thread or running it in on the thread pool when using a goroutine.
  • C# conversions attempt to make code visually similar to original Go code to make it easier to identity corresponding functionality. As Go is a minimalist language, it provides high-level functionality provided by the compiler, often much more than C# does. As such, converted C# code will have more visible code than Go for equivalent functionality, however much of this code will be behind the scenes in separate files using partial class functionality.
• Convert Go units test to C# and verify results are the same (TBD).
  • For most unit tests defined in Go, it should be possible to create an equivalent converted C# unit test. In many cases it may also be possible to successfully compare “outputs” of both unit tests as an additional validation test.
• Convert Go code into managed C# code.
  • Conversion always tries to target managed code, this way code is more portable. If there is no possible way for managed code to accomplish a specific task, an option always exists to create a native interop library that works on multiple platforms, i.e., importing code from a .dll/.so/.dylib. Even so, the philosophy is to always attempt to use managed code, i.e., not to lean towards native code libraries, regardless of possible performance implications. Simple first.

Project Status

Automated Code Conversion of Go Standard Library

A few initial conversions of the full Go source code have been completed, you can find the latest results in the repo: src/go-src-converted. These conversion successes are notable milestones in that they represent full successful conversions of the entire Go source library using the ANTLR4 Golang grammar without failing. Each iteration improves on the next, here are few examples:

• errors/errors.go => errors/errors.cs
• fmt/format.go => fmt/format.cs
• compress/gzip/gunzip.go => compress/gzip/gunzip.cs

Not all converted standard library code will compile yet in C# yet - work remaining to properly parse and convert all Go source library files, with its many use cases and edge cases, can be inferred by examining the warnings in the build log for this initial conversion. This log should help lay out a road map of remaining tasks.

Note that go2cs simple conversions currently depend on a small subset of the Go source library, src/gocore, that was manually converted. As the project progresses, there will be a merger of automatically converted code and manually converted code. For example, the builtin Go library functions will always require some special attention since many of its features are implemented outside normal Go code, such as with assembly routines.

A strategy to automate conversion of native system calls in Go code, i.e., a function declaration without a body that provides a signature for a native external function, is to create a partial method in C# for the native call. A manually created file that implements the partial method can now be added that will exist along side the auto-converted files and not be overwritten during conversion.

Recent Activity

Converted code now targets .NET 6.0 and C# 10.0. Recent updates use file-scoped namespaces, reduced indentation to better match original Go code and new command line options to control code styling and allow older C# versions.

Currently, work to improve code conversions is progressing by walking through each of the behavioral testing projects. Iterating through each of these simple use cases improves overall automated code conversion quality.

Sets of common Go sample code have been manually converted to C# using the current C# Go Library. As an example, all relevant code samples from the “Tour of Go” have been converted to C#, see converted code. Ultimately would like to see this in head-to-head mode using Try .NET, for example: Currently converted code will not execute with latest release of Try .NET (see posted issue). Will be watching for an update.

As releases are made for updated go2cs executables, this will also include updates to pre-converted Go Standard Library libraries for reference from NuGet.

Testing

Before attempting conversions it is important that Go coding environment is already properly setup, especially GOPATH environmental variable. See Getting Started with Go.

Current Go to C# code conversions reference compiled assemblies of the go2cs core library code from the configured GOPATH, specifically %GOPATH%\src\go2cs\. Run the deploy-gocore.bat script located in the go2cs\src folder to handle copying source to target path and then building needed debug and release assemblies.

Once a compiled version of the current go2cs core library has been deployed, you can test conversions. For example:

go2cs -o -i C:\Projects\go2cs\src\Tests\Behavioral\ArrayPassByValue

This will convert Go code to C#. You can then build and run both the Go and C# versions and compare results.

Debugging with Visual Studio: After running the deploy-gocore.bat script you can run conversion code from within Visual Studio by right-clicking on the go2cs project, selecting “Properties” then clicking on the “Debug” tab. In the “Application arguments:” text box you can enter the command line test parameters, e.g., -o -i -h C:\Projects\go2cs\src\Tests\Behavioral\ArrayPassByValue. When the active solution configuration targets “Debug” you can run the go2cs project to convert Go code, then run converted code.

Debugging Note: Keep in mind that you have local gocore source code and a copy of the source in the GOPATH. Compiled versions of converted code will reference the gocore code copy in the GOPATH folder. If you encounter an exception in gocore while debugging, Visual Studio will be displaying the code in the GOPATH folder. Any code changes you make might make will then be in the GOPATH folder instead of your local folder and be lost at the next run of the deploy-gocore.bat script.

Installation

There is an experimental release available, however, for latest updates you can compile the source code to produce a go2cs executable.

Copy the go2cs executable into the %GOBIN% or %GOPATH%\bin path. The go2cs can compile as a standalone executable for your target platform with no external dependencies using Visual Studio, see publish profiles.

Usage

Before posting an issue for usage related questions consider using the go2cs discussions forum.

1. Make sure source application already compiles with Go (e.g., go build) before starting conversion. That means any needed dependencies should already be downloaded and available, e.g., with go get.

2. Execute go2cs specifying the Go source path or specific file name to convert. For example:

   • Convert a single Go file: go2cs -l Main.go
   • Convert a Go project: go2cs MyProject
   • Convert Go Standard Library: go2cs -s -r C:\\Go\src\\

Command Line Options

Option	Description
-l	(Default: false) Set to only convert local files in source path. Default is to recursively convert all encountered “import” packages.
-o	(Default: false) Set to overwrite, i.e., reconvert, any existing local converted files.
-i	(Default: false) Set to overwrite, i.e., reconvert, any existing files from imported packages.
-h	(Default: false) Set to exclude header conversion comments which include original source file path and conversion time.
-t	(Default: false) Set to show syntax tree of parsed source file.
-e	(Default: $.^) Regular expression to exclude certain files from conversion, e.g., “^.+_test\.go$”. Defaults to exclude none.
-s	(Default: false) Set to convert needed packages from Go standard library files found in “%GOROOT%\src”.
-r	(Default: false) Set to recursively convert source files in subdirectories when a Go source path is specified.
-m	(Default: false) Set to force update of pre-scan metadata.
-u	(Default: false) Set to only update pre-scan metadata and skip conversion operations.
-g	(Default: %GOPATH%\src\go2cs) Target path for converted Go standard library source files.
-c	(Default: false) Set to target legacy compatible code, e.g., block scoped namespaces. Required for code sets prior to C# 10.
-a	(Default: false) Set to use ANSI brace style, i.e., start brace on new line, instead of K&R / Go brace style.
-k	(Default: false) Set to skip check for “+build ignore” directive and attempt conversion anyway.
-C	(Default: false) Set to convert CGO files, i.e., skip check for "+build cgo" directive or import “C” and attempt conversion anyway.
-O	(Default: false) Set to convert Go OS targeted files, i.e., skip check for OS target file name suffixes and attempt conversion anyway.
-A	(Default: false) Set to convert Go architecture targeted files, i.e., skip check for architecture target file name suffixes attempt conversion anyway.
‑‑help	Display this help screen.
‑‑version	Display version information.
value 0	Required. Go source path or file name to convert.
value 1	Target path for converted files. If not specified, all files (except for Go standard library files) will be converted to source path.

Future Options

A new command line option to prefer explicit types over var would be handy, e.g., specifying -x would request explicit type definitions; otherwise, without applying setting, conversion would default to using var where possible.

If converted code ever gets manually updated, e.g., where a new import is added, a command line option that would “rescan” the imports in a project and augment the project file to make sure all the needed imports are referenced could be handy.

C# to Go?

If you were looking to “go” in the other direction, a full code based conversion from C# to Go is currently not an option. Even for the most simple projects, automating the conversion would end up being a herculean task with so many restrictions that it would likely not be worth the effort. However, for using compiled .NET code from within your Go applications you have options:

1. For newer .NET Core applications, I would suggest trying the following project from Matias Insaurralde: https://github.com/matiasinsaurralde/go-dotnet – this codes uses the CLR Hosting API which allows you to directly use .NET based functions from within your Go applications.

2. For traditional .NET applications, a similar option would be to use cgo to fully self-host Mono in your Go application, see: http://www.mono-project.com/docs/advanced/embedding/.

Background

For more background information, see here.