[main] Add -- cmd flag separator to start different Gost processes

cmd/gost/main.go

@@ -7,6 +7,10 @@ import (
 	_ "net/http/pprof"
 	"os"
 	"os/signal"
+	"os/exec"
+	"strings"
+	"sync"
+	"context"
 	"runtime"
 	"syscall"
 
@@ -30,6 +34,45 @@ var (
 	metricsAddr  string
 )
 
+func init() {
+	args := strings.Join(os.Args[1:], "  ")
+
+	if strings.Contains(args, " -- ") {
+		var (
+			wg sync.WaitGroup
+			ret int
+		)
+
+		ctx, cancel := context.WithCancel(context.Background())
+
+		for wid, wargs := range strings.Split(" " + args + " ", " -- ") {
+			wg.Add(1)
+			go func(wid int, wargs string) {
+				defer wg.Done()
+				defer cancel()
+				worker(wid, strings.Split(wargs, "  "), &ctx, &ret)
+			}(wid, strings.TrimSpace(wargs))
+		}
+
+		wg.Wait()
+
+		os.Exit(ret)
+	}
+}
+
+func worker(id int, args []string, ctx *context.Context, ret *int) {
+	cmd := exec.CommandContext(*ctx, os.Args[0], args...)
+
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	cmd.Env = append(os.Environ(), fmt.Sprintf("_GOST_ID=%d", id))
+
+	cmd.Run()
+	if cmd.ProcessState.Exited() {
+		*ret = cmd.ProcessState.ExitCode()
+	}
+}
+
 func init() {
 	var printVersion bool