python driver and go stub; execute Go from Python

driver.py

import subprocess

cmd = ['./stub']
proc = subprocess.Popen(
        cmd,
        stdin=subprocess.PIPE,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE
      )

def consume(std, fn):
  while True:
    line = std.readline()
    if not line:
      break
    fn(line)

printer = lambda bs: print(b'-->' + bs)

# To avoid deadlocks: careful to: add \n to output, flush output, use
# readline() rather than read()
proc.stdin.write(b'{"fruta": 33}\n')
proc.stdin.flush()
print(proc.stdout.readline())

proc.stdin.write(b'{"fruta": 66}\n')
proc.stdin.flush()
print(proc.stdout.readline())

proc.stdin.write(b'{"fruta": -1}\n')
proc.stdin.flush()

consume(proc.stderr, printer)

consume(proc.stdout, printer)

proc.stdin.close()
proc.terminate()
proc.wait(timeout=0.2)

stub.go

package main

/*
go build stub.go
*/

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

type MedicalRecord struct {
	Fruta int `json:"fruta"`
}

func main() {
	var record MedicalRecord

	for {
		err := json.NewDecoder(os.Stdin).Decode(&record)
		if err != nil {
			log.Fatal(err)
		} else {
			fmt.Printf("ok: parsed %d\n", record.Fruta)
			if record.Fruta == -1 {
				fmt.Println("bye bye")
				fmt.Fprintf(os.Stderr, "forbidden number: %d\n", record.Fruta)
				fmt.Fprintf(os.Stderr, "yada yada\n")
				return
			}
		}
	}
}