wazero lets you run WebAssembly modules with zero platform dependencies. Since wazero doesn’t rely on CGO, you keep portability features like cross compilation. Import wazero and extend your Go application with code written in any language!

Here's an example of using wazero to invoke a Fibonacci function included in a Wasm binary.

While our source for this is TinyGo, it could have been written in another language that targets Wasm, such as Rust.

func Test_fibonacci(t *testing.T) {
	binary, _ := os.ReadFile("wasm/fibonacci.wasm")
	mod, _ := wasm.DecodeModule(binary)
	store := wasm.NewStore(wazeroir.NewEngine())
	store.Instantiate(mod, "test")

	for _, c := range []struct {
		in, exp int32
	}{
		{in: 20, exp: 6765},
		{in: 10, exp: 55},
		{in: 5, exp: 5},
	} {
		ret, retTypes, err := store.CallFunction("test", "fibonacci", uint64(c.in))
		require.NoError(t, err)
		require.Len(t, ret, len(retTypes))
		require.Equal(t, wasm.ValueTypeI32, retTypes[0])
		require.Equal(t, c.exp, int32(ret[0]))
	}
}

wazero is an early project, so APIs are subject to change until version 1.0.

The wazero runtime passes all the Wasm Spec test suites and is fully compatible with the WebAssembly v1.0 Specification.

If you want to provide Wasm host environments in your Go programs, currently there's no other choice than using CGO and leveraging the state-of-the-art runtimes written in C++/Rust (e.g. V8, Wasmtime, Wasmer, WAVM, etc.), and there's no pure Go Wasm runtime out there. (There's only one exception named wagon, but it was archived with the mention to this project.)

First of all, why do you want to write host environments in Go? You might want to have plugin systems in your Go project and want these plugin systems to be safe/fast/flexible, and enable users to write plugins in their favorite lanugages. That's where Wasm comes into play. You write your own Wasm host environments and embed Wasm runtime in your projects, and now users are able to write plugins in their own favorite lanugages (AssembyScript, C, C++, Rust, Zig, etc.). As an specific example, you maybe write proxy severs in Go and want to allow users to extend the proxy via Proxy-Wasm ABI. Maybe you are writing server-side rendering applications via Wasm, or OpenPolicyAgent is using Wasm for plugin system.

However, experienced Golang developers often avoid using CGO because CGO is not Go -- Rob Pike, and it introduces another complexity into your projects. But unfortunately, as I mentioned there's no pure Go Wasm runtime out there, so you have to resort to CGO.

Currently any performance optimization hasn't been done to this runtime yet, and the runtime is just a simple interpreter of Wasm binary. That means in terms of performance, the runtime here is infereior to any aforementioned runtimes (e.g. Wasmtime) for now.

However theoretically speaking, this project have the potential to compete with these state-of-the-art JIT-style runtimes. The rationale for that is it is well-know that CGO is slow. More specifically, if you make large amount of CGO calls which cross the boundary between Go and C (stack) space, then the usage of CGO could be a bottleneck.

Luckily with unsafe pointer casts, we can do JIT compilation purely in Go (e.g. https://github.com/bspaans/jit-compiler), so if we develop JIT Wasm compiler in Go without using CGO, this runtime could be the fastest one for some usecases where we have to make large amount of CGO calls (e.g. Proxy-Wasm host environment, or request-based plugin systems).

So as a long-term goal for this project, we are planning to add lowering of Wasm binary into more efficient and powerful format, and a JIT compilation engine purely written in Go.