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Go

How to install and use the Extism Go PDK​

Installation​

go get github.com/extism/go-pdk

Compiling to WebAssembly​

Install the TinyGo compiler and run:

tinygo build -o example.wasm -target wasi main.go

NOTE: Currently all Go plugins must be compiled targeting WASI. Active work is being done to remove this requirement.

Latest Docs​

https://pkg.go.dev/github.com/extism/go-pdk

Example Usage​

Using Config, I/O, & Persisted Variables​

main.go
package main

import (
    "strconv"

    "github.com/extism/go-pdk"
)

//export count_vowels
func count_vowels() int32 {
    input := pdk.Input()

    count := 0
    for _, a := range input {
        switch a {
        case 'A', 'I', 'E', 'O', 'U', 'a', 'e', 'i', 'o', 'u':
            count++
        default:
        }
    }

    // test some extra pdk functionality
    if pdk.GetVar("a") == nil {
        pdk.SetVar("a", []byte("this is var a"))
    }
    varA := pdk.GetVar("a")
    thing, ok := pdk.GetConfig("thing")

    if !ok {
        thing = "<unset by host>"
    }

    output := `{"count": ` + strconv.Itoa(count) + `, "config": "` + thing + `", "a": "` + string(varA) + `"}`
    mem := pdk.AllocateString(output)

    // zero-copy output to host
    pdk.OutputMemory(mem)

    return 0
}

func main() {}

Using Extism built-in HTTP​

http.go
package main

import (
    "github.com/extism/go-pdk"
)

//export http_get
func http_get() int32 {
    // create an HTTP Request (withuot relying on WASI), set headers as needed
    req := pdk.NewHTTPRequest("GET", "https://jsonplaceholder.typicode.com/todos/1")
    req.SetHeader("some-name", "some-value")
    req.SetHeader("another", "again")
    // send the request, get response back (can check status on response via res.Status())
    res := req.Send()

    // zero-copy output to host
    pdk.OutputMemory(res.Memory())

    return 0
}

func main() {}