Use execve to reuse the memory. Add a note about init

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.12-alpine as build
+FROM golang:1.13-alpine as build
 
 RUN apk update && apk add git
 

README.md

@@ -5,8 +5,10 @@ SSM Parent
 
 This is mostly a parent process for Docker with one addition: it can read from AWS SSM Parameter store.
 
+Please note, that it still requires a proper `init` process, for example the one embedded into Docker can be used with `docker run --init`.
+
 The way it works is that ssm-parent can be used as an entrypoint for Docker. Firstly, it retrieves all specified parameters, then injects them to the environment,
-and finally runs the command.
+and finally runs the command using `execve` syscall.
 
 All parameters must be in JSON format, i.e.:
 

cmd/run.go

@@ -4,6 +4,7 @@ import (
 	"os"
 	"os/exec"
 	"os/signal"
+	"syscall"
 
 	"github.com/springload/ssm-parent/ssm"
 
@@ -43,34 +44,18 @@ var runCmd = &cobra.Command{
 		if err != nil {
 			ctx.WithError(err).Fatal("Cant find the command")
 		}
+		cmdArgs = append(cmdArgs, args[:1]...)
 
 		c := make(chan os.Signal, 1)
 		signal.Notify(c)
 		if expand {
-			cmdArgs = ssm.ExpandArgs(args[1:])
+			cmdArgs = append(cmdArgs, ssm.ExpandArgs(args[1:])...)
 		} else {
-			cmdArgs = args[1:]
+			cmdArgs = append(cmdArgs, args[1:]...)
 		}
-
-		cmd := exec.Command(command, cmdArgs...)
-		cmd.Stdin = os.Stdin
-		cmd.Stdout = os.Stdout
-		cmd.Stderr = os.Stderr
-		cmd.Env = os.Environ()
-
-		if err := cmd.Start(); err != nil {
+		if err := syscall.Exec(command, cmdArgs, os.Environ()); err != nil {
 			ctx.WithError(err).Fatal("Can't run the command")
 		}
-
-		go func() {
-			for sig := range c {
-				cmd.Process.Signal(sig)
-			}
-		}()
-
-		if err := cmd.Wait(); err != nil {
-			ctx.WithError(err).Fatal("The command exited with an error")
-		}
 	},
 }