Load and Run Go WebAssembly Module

When I tried to write and run my first Go WebAssembly module, it seemed to be a easy task. I searched load wasm module that led me to the tutorial on MDN [1]. It looks easy, just use WebAssembly.instantiateStreaming() method and everything is done. But life is not so easy. It did not work. So I took a look at what other people did in their first Go wasm try (see references in [2]) and found out the solution.

To load and run compiled Go wasm module, we need a JavaScript loader provided in Go source. We can copy the JavaScript loader to current directory by the following shell command:

$ cp "$(go env GOROOT)/misc/wasm/wasm_exec.js" .

You can also download wasm_exec.js from Go GitHub repo.

Next, put wasm_exec.js, compiled Go wasm module (assume the name of the module is mymodule.wasm) and HTML file in the same directory. Insert the following code in the HTML file.

<script src="wasm_exec.js"></script>
<script>
      const go = new Go();
      let mod, inst;
      WebAssembly.instantiateStreaming(
              fetch("mymodule.wasm", {cache: 'no-cache'}), go.importObject).then((result) => {
              mod = result.module;
              inst = result.instance;
              run();
      });
      async function run() {
              await go.run(inst);
      };
</script>

Open the HTML with your browser and now you will see Go wasm code loaded and running!

Tested on:

• Ubuntu Linux 18.04
• Go 1.11.1
• Chromium Version 69.0.3497.81 on Ubuntu 18.04 (64-bit)

References: