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Using the Go Host SDK

Check your installation

Please be sure you've installed Extism before continuing with this guide.

1. Install the Go module​

Install via go get:

go get github.com/extism/extism

2. Import the module and use the APIs​

Count Vowels Plugin

code.wasm in this example is our example plugin that counts vowels. If you want to run this, download it first and set the path:

curl https://raw.githubusercontent.com/extism/extism/main/wasm/code.wasm > code.wasm
main.go
package main

import (
    "encoding/json"
    "fmt"
    "os"

    "github.com/extism/extism"
)

func main() {
    ctx := extism.NewContext()
    defer ctx.Free() // this will free the context and all associated plugins

    // set some input data to provide to the plugin module
    var data []byte
    if len(os.Args) > 1 {
        data = []byte(os.Args[1])
    } else {
        data = []byte("testing from go -> wasm shared memory...")
    }

    manifest := extism.Manifest{Wasm: []extism.Wasm{extism.WasmFile{Path: "../wasm/code.wasm"}}}
    plugin, err := ctx.PluginFromManifest(manifest, false)
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }

    // use the extism Go library to provide the input data to the plugin, execute it, and then
    // collect the plugin state and error if present
    out, err := plugin.Call("count_vowels", data)
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }

    // "out" is []byte type, and the plugin sends back json, so deserialize it into a map.
    // expect this object: `{"count": n}`
    var dest map[string]int
    json.Unmarshal(out, &dest)

    fmt.Println("Count:", dest["count"])
}

Other Documentation​

See the module documentation at: https://pkg.go.dev/github.com/extism/extism

Need help?​

If you've encountered a bug or think something is missing, please open an issue on the Extism GitHub repository.

There is an active community on Discord where the project maintainers and users can help you. Come hang out!