some changes

internal/worker/run.go

@@ -1,25 +1,49 @@
 package worker
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
 	"os/exec"
 )
 
-func RunFunction(path string, fc *FuncConfig, input []byte) ([]byte, error) {
-	if fc.Runtime != "exec" {
-		return nil, fmt.Errorf("unsupported runtime: %s", fc.Runtime)
+type RunOps struct {
+	Log        Logger
+	Path       string
+	FuncConfig *FuncConfig
+	Env        []string
+}
+
+func RunFunction(opt *RunOps, input []byte) ([]byte, error) {
+	if opt.FuncConfig.Runtime != "exec" {
+		return nil, fmt.Errorf("unsupported runtime: %s", opt.FuncConfig.Runtime)
 	}
 
-	cmd := exec.Command(path)
+	cmd := exec.Command(opt.Path)
+	cmd.Env = opt.Env
 	cmd.Stdin = bytes.NewReader(input)
 
 	var out bytes.Buffer
 	cmd.Stdout = &out
-	cmd.Stderr = &out
+	stderrPipe, err := cmd.StderrPipe()
+	if err != nil {
+		return nil, err
+	}
+	go func() {
+		scanner := bufio.NewScanner(stderrPipe)
+		for scanner.Scan() {
+			line := scanner.Text()
+			opt.Log.Write(line)
+		}
+	}()
 
-	if err := cmd.Run(); err != nil {
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+
+	if err := cmd.Wait(); err != nil {
 		return nil, fmt.Errorf("failed: %w\noutput: %s", err, out.String())
 	}
+
 	return out.Bytes(), nil
 }