Skip to main content
Version: 1.x

Go Component SDK with Custom WIT

This example is a WebAssembly component that demonstrates how to use the wasmCloud Go Component SDK in conjunction with your own custom WIT interfaces.

You can find this application's custom interface in wit/world.wit:

wit
interface invoker {
  call: func() -> string;
}

📦 Dependencies​

[!WARNING] Due to incompatibilities introduced in wasm-tools v1.226.0, a version of wasm-tools <= 1.225.0 is required for running this example.

You can install wasm-tools v1.225.0 from upstream releases, or use cargo (Rust toolchain) if installed to install 1.225.0 -- (i.e. cargo install --locked wasm-tools@1.225.0)

Before starting, ensure that you have the following installed in addition to the Go (1.23+) toolchain:

👟 Run the example​

Clone the wasmCloud/go repository:

shell
git clone https://github.com/wasmCloud/go.git

Change directory to examples/component/invoke:

shell
cd examples/component/invoke

In addition to the standard elements of a Go project, the example directory includes the following files and directories:

  • build/: Target directory for compiled .wasm binaries
  • gen/: Target directory for Go bindings of interfaces
  • wit/: Directory for WebAssembly Interface Type (WIT) packages that define interfaces
  • bindings.wadge_test.go: Automatically generated test bindings
  • wadm.yaml: Declarative application manifest
  • wasmcloud.lock: Automatically generated lockfile for WIT packages
  • wasmcloud.toml: Configuration file for a wasmCloud application

Build the component​

We will build and deploy this example manually, since we will be using the wash call subcommand to interact with the application, requiring a stable identity to call. (As you gain experience with wasmCloud, you will likely want to use the wash dev subcommand to automate your development process.)

Build the component:

shell
wash build

Start a wasmCloud environment​

Start a local wasmCloud environment (using the -d/--detached flag to run in the background):

shell
wash up -d

Deploy the application​

Deploy the component using the application manifest (wadm.yaml):

shell
wash app deploy wadm.yaml

To ensure that the application has reached Deployed status, you can use wash app list:

shell
wash app list

Invoke the component​

Once the application is deployed, you can call the component using the wash call subcommand, which invokes a function on a component:

shell
wash call invoke_example-invoker example:invoker/invoker.call
text
Hello from the invoker!

Clean up​

You can delete an application from your wasmCloud environment by referring either to its application name (invoke-example) or the original application manifest:

shell
wash app delete wadm.yaml

Stop your local wasmCloud environment:

shell
wash down

Bonus: Calling when running with wash dev​

When running with wash dev, wasmCloud uses a generated ID for the component. If you have jq installed, you can run the following command to call the component:

bash
wash call "$(wash get inventory -o json | jq -r '.inventories[0].components[0].id')" example:invoker/invoker.call
Hello from the invoker!

📖 Further reading​

For more on custom interfaces, see the Interface Developer Guide in the wasmCloud documentation.