Running Go Programs as IBM Cloud Functions

Showing not telling

I’ll illustrate the capability by writing a program in Go and running it using IBM Cloud Functions. The source below is a variant of an example I’ve used before to explain Docker actions.

package main

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

func main() {

    // program receives one argument: the JSON object as a string
    arg := os.Args[1]

    // unmarshal the string to a JSON object
    var obj map[string]interface{}
    json.Unmarshal([]byte(arg), &obj)

    // can optionally log to stdout (or stderr) 
    fmt.Println("hello Go action")

    name, ok := obj["name"].(string)
    if !ok { name = "Stranger" }

    // last line of stdout is the result JSON object as a string
    msg := map[string]string{"msg": ("Hello, " + name + "!")}
    res, _ := json.Marshal(msg)
    fmt.Println(string(res))
}

Save the code above to a file sample.go and build it. You must set the GOOS and GOARCH properties to cross-compile the binary if you build the binary on another platform. The executable must be called exec.

GOOS=linux GOARCH=amd64 go build -o exec

The rest is standard OpenWhisk workflow to create an action. The executable must be Zip compressed. And the action is created using the --native parameter to indicate this is a native executable using the wsk command line interface.

zip exec.zip exec
wsk action create helloGo --native exec.zip

The action is invoked as any other action.

$ wsk action invoke helloGo -r -p name Gopher 
{
    "msg": "Hello, Gopher!"
}