Go Tooling

This guide walks through building a Go component that implements the adder world defined in the adder/world.wit package. The component will implement the adder world, which contains an add interface with an add function.

Keep in mind that this is a basic intro. For more examples, please see the componentize-go repository examples.

If you still have questions, feel free to reach out to to the componentize-go maintainers on Zulip or open an issue on the repository.

1. Install the tools

• Go 1.25.5+
• componentize-go Latest version

2. Create your Go project

With the component-docs repository cloned locally, run the following:

mkdir go-adder && cd go-adder

2. Determine which world the component will implement

Since we will be implementing the adder world, we can copy the WIT to our project. Create a subdirectory called wit and paste the following code into a file called wit/adder.wit:

package docs:adder@0.1.0;

interface add {
    add: func(x: u32, y: u32) -> u32;
}

world adder {
    export add;
}

3. Generate bindings for the Wasm component

Run the following commands to generate bindings for the component:

componentize-go --world adder bindings
go mod tidy

The project directory will look like this:

$ tree
.
├── go.mod
├── go.sum
├── wit
│   └── adder.wit
└── wit_exports.go

Here’s a breakdown of what each of these files do:

• go.mod contains a required library of shared WIT types (see go.bytecodealliance.org/pkg)
• wit_exports.go defines the //go:wasmexport methods for the Go WebAssembly compiler.

If you try to compile this, you’ll get an error from the wit_exports.go file:

could not import wit_component/export_docs_adder_add (no required module provides package "wit_component/export_docs_adder_add")

We’ll create this module in the next section.

4. Implement the add Function

In your add directory, create a file called export_docs_adder_add/exports.go and paste the following code into it:

package export_docs_adder_add

func Add(x uint32, y uint32) uint32 {
	return x + y
}

5. Build the Component

To compile your Go application to WebAssembly, run the following command:

componentize-go build

This will output a main.wasm file that will be run in the next section.

5. Testing the add Component

To verify that our component works, let’s run it from a Rust application that knows how to run a component targeting the adder world. Be sure to have the Rust toolchain installed.

The application uses wasmtime to generate Rust “host”/“embedder” bindings, bring in WASI worlds, and execute the component.

From within the go-adder directory, run the following:

$ cd ../component-model/examples/example-host
$ cargo run --release -- 1 2 ../../../go-adder/main.wasm
1 + 2 = 3

With this, we have successfully built and run a basic WebAssembly component with Go 🎉