This server in go allows you to make an HTTP request to an endpoint and pass the body content as STDIN input to a command line script and return the output.

command-execution-server.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os/exec"
)

func main() {
	http.HandleFunc("/webcmd", func(w http.ResponseWriter, r *http.Request) {

		b, err := ioutil.ReadAll(r.Body)
		txt := string(b)
		log.Println(txt)

		/* You can use query parameters to get a dynamic script
		 * but here I just use a hardcoded one.
		 *
		 * queryValues := r.URL.Query()
		 * script := queryValues.Get("script")
		 */
		cmd := exec.Command("/path/to/the/script/to/execute")

		stdin, err := cmd.StdinPipe()
		defer stdin.Close()
		if err != nil {
			log.Fatalln(err)
		}
		_, err = stdin.Write([]byte(txt))
		if err != nil {
			log.Fatalln(err)
		}

		out, err := cmd.Output()
		if err != nil {
			log.Fatalln(err)
		}
		log.Println(string(out))

		fmt.Fprintf(w, "%v", string(out))
	})

	// Uncomment to enable a file server too
	//fs := http.FileServer(http.Dir("."))
	//http.Handle("/", fs)

	log.Fatal(http.ListenAndServe(":11111", nil))
}